Teeing Ground
Order of play
Falling off tee

Playing the Ball
Unplayable
Wrong, Substitute
Lifting, dropping
Moved, deflected

Provisional, Lost, Out of bounds

Putting Green
Flagstick
Marking, lifting
Stymie

Hazards
Water hazards
Lateral water hazards

Abnormal Conditions
GUR
Casual water
Hole, cast, or runway

Obstructions,
Loose impediments

Miscellaneous
Rule 1
Advice
Scoring
Stableford
Rule 3-3
Old Course, St Andrews
Wartime local rules
Best ever golf poem

FORE!
I have read many times on the internet that the origin of "Fore" was a cry to alert the forecaddie that a player's ball was on its way. I have not seen any good evidence to support that explanation, but I'm open to persuasion...

In the meantime, I have come across a couple of pieces which tend to support another, more plausible, idea that the shout was a warning to anyone ahead, much like its use today:

From the 1875 Rules:

To prevent accidents, it is required that due warning be given to all parties on or in the vicinity of the golfing course, by the player or his caddie distinctly calling "Fore" previous to his striking the ball.

From an article on the Mr Golf Etiquette website (courtesy of Jim Corbett):

The Oxford English Dictionary says that the word "fore" used in a golf context is probably a contraction for "Before." It cites the first written use of the term in 1878 as, "A warning cry to people in front of the stroke."

"Dr. Neilson, a keen student of Scottish history and literature, discovered a passage in the works of John Knox which, shorn of the eccentricities of sixteenth-century spelling, reads as follows:
'One among many comes to the East Port (i.e., gate) of Leith, where lay two great pieces of ordnance, and where their enemies were known to be, and cried to his fellows that were at the gate making defence: "Ware Before!" and so fires one great piece, and thereafter the other.'  The cry of 'Beware before' -- Look out in front -- was, of course, the signal for the defenders of the gate to drop to the ground in order that the guns might be fired over them.
The situation is not dissimilar to that of the golfer intending to drive over the head of someone on the fairway in front, and the way in which the military signal 'Ware before!' might in the course of time be cut down to "Fore!" needs no explaining.  'Look out in front!'  It is the most democratic of shouts, which no one dares to let pass unheeded.  During an Open Championship at Sandwich many summers ago, I saw a future King of England scurrying apologetically off the fairway in response to a distant bellow of "Fore!" from one of our less distinguished professionals."

The USGA has wrestled with the stroke-and-distance penalty for a ball lost or out of bounds (Rule 27-1) for many years. In the 1960s the USGA completed what Richard S. Tufts, a past president of the USGA, termed a "noble experiment" in the evolution of the Rules. In a dramatic move away from the Royal and Ancient Golf Club -- and a unified code -- the USGA adopted experimental Rules for 1960 and '61.

"Frequent Rules changes, especially on a trial basis, are generally undesirable," John M. Winters Jr., then chairman of the Rules of Golf Committee, wrote in the February 1961 issue of Golf Journal. "But an open mind and a willingness to venture into new areas can be productive in any activity.

"Not so long ago the Rules did not recognize lateral water hazards; now they receive special treatment in the Rules. The 14-club Rule was not introduced until 1938; it is now a fundamental. The abolition of the stymie was an outgrowth of various experiments."

So, too, was this trial, which had roots back to the mid-1940s. Before 1946, a lost ball, a ball out of bounds and a ball unplayable suffered the same fate: stroke-and-distance. From 1946 to 1951, however, the penalty for a ball out of bounds was distance only (e.g., if you hit your tee shot out of bounds, you would be playing your second stroke from the tee). It is interesting to note that during this period, a player was better off hitting a shot out of bounds than hitting one into a large bush as the only procedure for a ball unplayable remained stroke and distance.

With the first unified Rules of Golf agreed upon by the USGA and the R&A for 1952, the penalty for a ball out of bounds reverted to stroke-and-distance. Another change was that the player was given a second option for a ball unplayable (the current Rule 28c), but it entailed a two-stroke penalty.

In 1960, the USGA broke away from the R&A with a trial Rule for one year, adopting the penalty of distance only for a ball lost or out of bounds. It was found that in many cases, the penalty of distance only was not severe enough for a lost ball. For example, a player who shanks a pitch shot into deep woods might well prefer to replay the stroke with loss of distance only rather than find his ball. In the USGA's view, any Rule which encourages a player not to find his ball is a weak Rule.

Stroke-and-distance returned in 1961, but the USGA was still somewhat uncomfortable with the penalty for a ball out of bounds. It authorized a Committee to adopt a Local Rule allowing a player to drop a ball, with a penalty stroke, within two club-lengths of the spot where the original ball last crossed the boundary, not nearer the hole. This Local Rule, which was allowed again in 1964-67, was intended for areas where the standard stroke-and-distance penalty would be unduly severe and only where it is not difficult to determine if a ball is out of bounds or where it last crossed the boundary.

This Local Rule was revoked in 1968 because, among other reasons, it abandoned the principle that like situations should be treated alike. For the purpose of a consistent application of the Rules, a ball that is out of bounds should be treated the same in all situations. Since it is often not known whether a lost ball is lost on the course or out of bounds, the penalty for a lost ball and a ball out of bounds must be the same. As there is no spot from which to measure two club-lengths with a lost ball, the only practical solution is to require the player to return to the spot from which he last played.

Is the stroke-and-distance procedure for a ball lost or out of bounds with us until Armageddon? Given the substantial changes in the Rules over their first 250 years, it would be foolhardy to dismiss anything. However, the discerning historian should not place any bets to the contrary.

Rub of the Green
(Courtesy of Richard Groff. You can read the full text of his article here)
The term “rub of the green” is defined in the Rules of Golf as the accidental deflection of a ball in motion by an outside agency. Despite this clarity, many argue that the term is more general, meaning “bad luck.” Thus, they might say, a ball that ends up in a hazard is a rub of the green. Despite this general belief, there is no authority for the proposition that “rub” in any context has a connection with luck, good or bad.

Where did it come from? The game of bowls has the probable answer.

Webster’s 1913 revised, unabridged dictionary defines “rub” as follows:

1. The act of rubbing; friction.
2. That which rubs; that which tends to hinder or obstruct motion or progress; hindrance; obstruction, an impediment; especially, a difficulty or obstruction hard to overcome; a pinch.
3. Inequality of surface, as of the ground in the game of bowls; unevenness.

The Oxford English Dictionary (1931) defines rub more specifically in the context of bowls:

An obstacle or impediment by which a bowl is hindered in, or diverted from its proper course; also the fact of the bowl meeting with such impediment.

The Universal Dictionary of the English Language (Colliers, 1897) provides a very interesting look at the meaning of the term in those times with specific reference to bowls:

3. To incline or turn in towards the jack.
4. Inequality of the ground which hinders the motion of the bowl.

The term “green” also causes some confusion to the modern student of the rules because in golf it has more than one meaning. However, it is clear that the “green” referred to in “rub of the green” means more than just the putting surface. The green in bowls was the entire playing area. The term “through the green” in golf expresses the same idea, with some limitation.

The OED defines green:

A piece of grassy land used for some particular purpose, as bleaching green, bowling green. In golf the putting ground, sometimes the whole links or field.

Conclusion.
The origin of the term “rub of the green” seems clear. The natural and expected curving of the bowl toward the jack is a rub. The movement of a bowl that is deflected by the uneven ground of the green is called a rub of the green. Adaptation of this concept to golf was natural because of the similarities in playing a ball to a target over a green. The idea that rub means bad luck simply has no support in the definition or early uses of the term. The sources make it clear that “rub” means to impede, interfere, obstruct. Such action may be bad luck, but the term does not mean that.

Scorecards
First mentioned in the rules of 1891.  The competitor was obliged to countersign his card for a brief period, 1899-1901, thereafter only the marker's signature was required until 1947 (USGA) and 1950 (R&A). 

Rule 1.
The whole idea of the game - to get a ball from the teeing ground into a hole - was written into the rules in 1891.  For some reason it fell outside the rules from 1933, and was stated only as a preamble to the definitions.  Re-incorporated into rule 1 in 1952.

Advice
From 1858 a player may not ask for advice, nor be knowingly advised except by his own side.  From 1908 advice was defined much as it is today but the clarification of public information and information on the Rules was added in 1933.

But giving unsolicited advice was apparently not an offence until 1947 (USGA) and 1952 (R&A).

Second ball in stroke play (now Rule 3-3)
In 1947 the USGA introduced a procedure which allowed a player to play a second ball, in stroke play only, if he was in doubt as to how to proceed.  The sole purpose of this rule was to allow a player to avoid disqualification. The rule was incorporated into the joint R&A and USGA code of 1952.
The second ball automatically counted if the rules allowed the procedure to be adopted, otherwise the first ball counted. This was changed in 1956, when the player must announce which ball he wants to score before putting the second ball into play; but failing to announce meant the second ball automatically counted.
In 1972 if the player failed to announce which ball he wanted to score, then the highest score counted. Changed in 1988 to original ball counts.

Caddies - (Courtesy of Tony McCrae)

1. No Boy under Eleven years of age shall be admitted as a Caddie.
   
2. Boys admitted as Caddies shall be required to continue their Education and also to attend a Sunday School.
   
3. Swearing, intemperance, dishonesty and the use of improper or uncivil language shall be strictly prohibited at all times on pain of dismissal.
   
4. All Boys admitted as Caddies shall be provided with a Cap, bearing the Club Badge which he must wear on the Links, so long as he is to be employed, and return to the Club, when he retires or is dismissed.
   
5. No Boy who engages himself to a Gentleman in the morning shall be allowed to break that engagement till the day's play is over, or if he does, shall forfeit half his forenoon's pay.
   
6. All Caddie Boys shall consider themselves as Boys till they reach the age of Eighteen years.
   
7. Messrs. Morris, Forgan, Wilson, and the Club Steward shall be appointed to fix upon the proper Boys to select as Caddies, to take a supervision of them, and to receive any complaints that have to be made and these to be remitted to the Green Committee for adjudication, and they having full power in this matter their sentence shall be final.
   
8. All Boys admitted as Caddies in the service shall have a copy of these Rules given them, and in the event of any contravention of them, the guilty party will be liable to suspension if not expulsion from the service.
   

Other snippets...
The first etiquette rule appeared in Aberdeen 1783: "While a Stroke is playing none of the Party shall walk about, make any motion, or attempt to take off the Player's attention, by speaking or otherwise".

1933 USGA recommends players put an identification mark on their ball.

Earliest reference to strokeplay was in 1759.

Practice on the course on Medal days (i.e. stroke competitions) was first prohibited by R&A 1829. The Honourable Company 1839, Perth 1839 and Blackheath 1844 also had this rule, the penalty being disqualification.
From 1886 (Royal IoW) and 1891 R&A the restriction was confined to practice on putting greens on the day of a stroke competition. Practice through the green was unrestricted until 1933, when players may not play to a hole 'within their reach'. Practice anywhere on the course was prohibited from 1950 (1952 in USGA); at the same time playing a practice stroke during play was also banned.

Richmond Golf Club Temporary Rules, 1941

This is nothing to do with the rules, but allow me a little indulgence.  John Betjeman, former Poet Laureate, is among my favourite poets.  If you have ever played on British Isles links, you will appreciate it immediately; if not, it must surely inspire you to go and do it...