Etymology
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so long (interj.)

parting salutation, 1860, of unknown origin, perhaps from a German idiom (compare German parting salutation adieu so lange, the full sense of which probably is something like "farewell, whilst (we're apart)"); or perhaps from Hebrew shalom (via Yiddish sholom). Some have noted a similarity to Scandinavian leave-taking phrases, such as Norwegian Adjø så lenge, Farvel så lenge, Mor'n så lenge, literally "bye so long, farewell so long, morning so long;" and Swedish Hej så länge "good-bye for now," with så länge "for now" attested since 1850 according to Swedish sources. Most etymology sources seem to lean toward the German origin. So long (adv.) "for such a long time" is from late Old English.

Earlier guesses that it was a sailors' corruption of a South Pacific form of Arabic salaam are not now regarded as convincing. "Dictionary of American Slang" also adds to the list of candidates Irish slán "safe," said to be used as a salutation in parting. The phrase seems to have turned up simultaneously in America, Britain, and perhaps Canada, originally among lower classes. First attested use is in title and text of the last poem in Whitman's "Leaves of Grass" in the 1860 edition.

An unknown sphere, more real than I dream'd, more direct, darts awakening rays about me — So long!
Remember my words — I may again return,
I love you — I depart from materials;
I am as one disembodied, triumphant, dead.

Whitman's friend and fan William Sloane Kennedy wrote in 1923:

The salutation of parting — 'So long!' — was, I believe, until recent years, unintelligible to the majority of persons in America, especially in the interior, and to members of the middle and professional classes. I had never heard of it until I read it in Leaves of Grass, but since then have quite often heard it used by the laboring class and other classes in New England cities. Walt wrote to me, defining 'so long' thus: "A salutation of departure, greatly used among sailors, sports, & prostitutes — the sense of it is 'Till we meet again,' — conveying an inference that somehow they will doubtless so meet, sooner or later." ... It is evidently about equivalent to our 'See you later.' The phrase is reported as used by farm laborers near Banff, Scotland. In Canada it is frequently heard; 'and its use is not entirely confined to the vulgar.' It is in common use among the working classes of Liverpool and among sailors at Newcastle-upon-Tyne, and in Dorsetshire. ... The London Globe suggests that the expression is derived from the Norwegian 'Saa laenge,' a common form of 'farewell,' au revoir. If so, the phrase was picked up from the Norwegians in America, where 'So long' first was heard. The expression is now (1923) often used by the literary and artistic classes.
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long shot (n.)
also long-shot, in the figurative sense of "something unlikely," 1867, from long (adj.) + shot (n.). The notion is of a shot at a target from a great distance, thus difficult to make. Cinematic sense is from 1922. As an adjective by 1975.
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big time (n.)
"upper reaches of a profession or pursuit," by 1909 in vaudeville slang. As an adjective by 1915. The same phrase was common in colloquial use late 19c.-early 20c. in a broad range of senses: "party, shindig, fun, frolic."
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long pig (n.)

"human being eaten as food," by 1848, in stories from the Fiji Islands, said to be a literal rendering of a local term, in one version puaka balava.

Bau literally stank for many days, human flesh having been cooked in every house, and the entrails thrown outside as food for pigs, or left to putrefy in the sun. The Somosomo people were fed with human flesh during their stay at Bau, they being on a visit at that time; and some of the Chiefs of other towns, when bringing their food, carried a cooked human being on one shoulder, and a pig on the other; but they always preferred the "long pig," as they call a man when baked. ["FEEJEE.—Extract of a Letter from the Rev. John Watsford, dated Ono, October 6th, 1846." in "Wesleyan Missionary Notices," Sept. 1847]
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long run (n.)

also long-run, "ultimate outcome," 1620s, from long (adj.) + run (n.); the notion is "when events have run their course," as in the phrase in the long run "after a long course of experience." As an adjective from 1804.

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time zone (n.)

by 1885, from time (n.) + zone (n.). As in Britain and France, the movement to regulate time nationally came from the railroads.

Previous to 1883 the methods of measuring time in the United States were so varied and so numerous as to be ludicrous. There were 50 different standards used in the United States, and on one road between New York and Boston, whose actual difference is 12 minutes, there were three distinct standards of time. Even small towns had two different standards one known as "town" or local time and the other "railroad" time.
... At noon on November 18, 1883, there was a general resetting of watches and clocks all over the United States and Canada, and the four great time zones, one hour apart, into which the country was divided came into being. So smoothly did the plan work that the general readjustment was accomplished without great difficulty and it has worked satisfactorily ever since. [Railroad Trainman, September 1909]
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long johns (n.)
type of long, warm underwear, 1943, originally made for U.S. GIs in World War II. Earlier as the name of a type of pastry (1919). Also used of sorts of worm, potato, table, sled, etc.
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charley horse (n.)
1887, sporting slang, origin obscure, probably from somebody's long-forgotten lame racehorse. Charley horse seems to have been a name for a horse or a type of horse (perhaps especially a lame one) around that time.
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lang syne 
"long ago," c. 1500, Scottish dialect variant of long since; popularized in Burns' song, 1788. Century Dictionary has langsyner "person who lived long ago."
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pro tempore 

"temporary," Latin, literally "for the time (being)," from pro "for" (see pro-) + ablative singular of tempus "time" (see temporal). Abbreviated form pro tem is attested by 1828.

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