The humorous phrase the nineteenth hole denotes the bar room in a golf clubhouse, as reached at the end of a standard round of eighteen holes.
These are, in chronological order, the earliest occurrences of the phrase that I have found—first in British English, then in American English:
IN BRITISH ENGLISH
1-: From The Evening Telegraph (Dundee, Angus, Scotland) of Friday 5th December 1890:
The Monifieth Club finish their golfing season tomorrow, when they play for medals, and a number of clubs, balls, and other prizes. With such inducements there ought to be a big turnout, but the shortness of the day will prevent many from getting around who would otherwise be on the green. They are to hold their annual supper shortly, when some of the members will be sure to exhibit as much, if not more, enthusiasm and heartiness at the “nineteenth” hole as they do on the green on cup and medal days.
2-: From The Cheshire Observer (Chester, Cheshire, England) of Saturday 6th June 1891:
On some golf courses they have a “nineteenth hole” in the shape of a public-house. Players always negotiate this hole at the first attempt.
3-: From the column Here and There, published in The Evening Telegraph (Dundee, Angus, Scotland) of Thursday 28th September 1893:
A discussion arose yesterday in the train from Monifieth to Dundee between some golfing friends of mine as to the direction of the wind. On the one side it was said to be blowing from the northeast, while the other declared it was the southeast. No settlement being arrived at it was arranged to refer the matter the “cardinal points” on the top of the Custom House. On their arrival at Dundee both sides were dumbfounded to find that which was to settle their dispute with its east “finger” pointing towards Perth and the west one to Tayport.
Whether it was that the cardinal points had got out of order or that the “nineteenth hole” had been too frequently visited was not definitely settled.
4-: From Our Volunteer Column, published in The Evening Telegraph (Dundee, Angus, Scotland) of Wednesday 4th October 1893:
A carbine team from the Dundee Artillery were the guests of No. 2 Company 1st Fife V.A. at Tayport on Saturday, and were entertained most hospitably—in fact, the hospitality of the Fifers only failed in one particular, and the Dundonians were in great measure to blame for that themselves.
The imperfection to which I refer was the beating they gave their visitors, but a slip like this will occur even in the best regulated corps.
[…] The meeting was a pleasant one, and the losers enjoyed themselves very much, at the butts and in the Drill Hall, which for this occasion had been rendered analogous to the nineteenth hole of the golfing fraternity.
IN AMERICAN ENGLISH
1-: From an article about the golf course at Van Cortlandt Park, New York City, published in The New York Times (New York City, N.Y., U.S.A.) of Sunday 21st May 1899:
Police Capt. Schmittberger is another of the prominent golfers, and he is accredited with a famous remark that has come to be one of the stock stories of the Van Cortlandt links. On the new part of the course which is now being laid out the eighteenth and last hole is near a roadhouse or saloon just across the road from the park property. A new golfhouse has been built near this place, and it is the intention, although many objections have been raised, to make it the general golf headquarters. Capt. Schmittberger, perhaps unconsciously, expressed the situation well when, after finishing a game one day, he remarked, “There’s the seventeenth hole back there, this is the home hole, and the nineteenth hole is across the way in Sullivan’s.”
2-: From the account of a golf tournament at “the new Fairmont six-hole course”, published in The Kansas City Star (Kansas City, Missouri, U.S.A.) of Sunday 2nd July 1899—here, the nineteenth hole denotes “a large elm tree”:
The practicality of the costumes did not prevent the greens from presenting a beautiful sight when the tournament was in full swing, with golfers playing at every hole and every tee and a bevy of summer dressed women gathered around the “nineteenth hole,” in this case a large elm tree where the tired tourist of the links could enjoy the welcome shade and talk learnedly of “foozles,” “stymies” and “bunkers.”
3-: From a description of “the Country club’s newly completed eighteen-hole golf course”, published in The Kansas City Star (Kansas City, Missouri, U.S.A.) of Tuesday 4th July 1899:
The sixteenth link is only 80 yards long, but the approach is over the pond and the hole is protected on all sides. A long carry back over the pond will help the ball towards seventeen, but the approach shot must be true, as tees surround the green on three sides. Then a good, strong drive over the brook and an approach over the road will land the ball on the home green and a tired pair of legs will carry the golfer to the “nineteenth hole,” there to play over the course again, but only in his mind.
4-: From an article about the cost of caddie service at “one of the local golf clubs”, published in The Daily Inter Ocean (Chicago, Illinois, U.S.A.) of Sunday 31st December 1899:
The club maintains that it loses considerable money each season on caddie checks which have to be paid, but the signature is so illegible that it cannot be deciphered, and the sum has to be charged to profit and loss. Perhaps some of the philanthropic members who do not wish to deprive the caddies of a percentage of their earnings and at the same time have the club suffer no loss may be good enough to start a movement to have the members improve their penmanship, or, better yet, have them sign their checks before reaching the nineteenth hole, which is popularly known as the bar. After that section of the clubhouse is reached it would take a decidedly better expert than Bertillon * to decipher the hieroglyphics which the writer would be ashamed to acknowledge as his signature the next morning.
* Alphonse Bertillon (1853-1914) was a French criminologist; he devised a system of body measurements for the identification of criminals.
The phrase is sometimes used figuratively—as in the following from the review of The Complete Works of Geoffrey Chaucer. Edited by F. N. Robinson (Boston: Houghton Mifflin Co., 1933)—review by M. B. Ruud, published in Modern Language Notes (Baltimore: The Johns Hopkins University Press) of May 1935:
Scholars in this country, who often, quite properly, are troubled by the state of higher studies in our universities and who in their own persons feel the intellectual life submerged in routine teaching, in committees, and in the nineteenth hole of one kind or another, have long taken comfort in the achievements of American Chaucerians.