"being but a single unit or individual; being a single person, thing, etc. of the class mentioned;" as a pronoun, "a single person or thing, an individual, somebody;" as a noun, "the first or lowest of the cardinal numerals; single in kind, the same; the first whole number, consisting of a single unit; unity; the symbol representing one or unity;" c. 1200, from Old English an (adjective, pronoun, noun) "one," from Proto-Germanic *ainaz (source also of Old Norse einn, Danish een, Old Frisian an, Dutch een, German ein, Gothic ains), from PIE root *oi-no- "one, unique."
Originally pronounced as it still is in only, atone, alone, and in dialectal good 'un, young 'un, etc.; the now-standard pronunciation "wun" began c. 14c. in southwest and west England (Tyndale, a Gloucester man, spells it won in his Bible translation), and it began to be general 18c. Its use as indefinite pronoun was influenced by unrelated French on and Latin homo.
Before the name of a person, indicating "hitherto unknown" or not known to the speaker.
One and only "sweetheart" is from 1906. Slang one-arm bandit for a type of slot machine is recorded by 1938. One-night stand is 1880 in performance sense; 1963 in sexual sense. One of the boys "ordinary amiable fellow" is from 1893. One-track mind "mind capable of only one line of thought or action" is by 1915. Drinking expression one for the road is from 1950 (as a song title). One-man band is by 1909 in a literal sense, 1914 figurative. One of those things "unpredictable occurrence" is from 1934 (Cole Porter's song is from 1935).
The conscience clause is one of the weaknesses of the Bill. It is one of those things which tend to create the bitterness. The conscience clause is one of those things which are inseparable from a Bill like this. It is one of those things which divides the sheep from the goats—members can pick them out for themselves—in the playground, in the school. ["Religious Exercises in School Bills," New Zealand Parliamentary Debates, Aug. 13, 1926]
1756, "special vocabulary of tramps or thieves," later "jargon of a particular profession" (1801). The sense of "very informal language characterized by vividness and novelty" is by 1818.
Anatoly Liberman writes here an extensive account of the established origin of the word from the Northern England noun slang "a narrow piece of land running up between other and larger divisions of ground" and the verb slanger "linger, go slowly," which is of Scandinavian origin (compare Norwegian slenge "hang loose, sling, sway, dangle," Danish slænge "to throw, sling"). "Their common denominator seems to be 'to move freely in any direction' " [Liberman]. Noun derivatives of these (Danish slænget, Norwegian slenget) mean "a gang, a band," and Liberman compares Old Norse slangi "tramp" and slangr "going astray" (used of sheep). He writes:
It is not uncommon to associate the place designated for a certain group and those who live there with that group’s language. John Fielding and the early writers who knew the noun slang used the phrase slang patter, as though that patter were a kind of talk belonging to some territory.
So the sense evolution would be from slang "a piece of delimited territory" to "the territory used by tramps for their wandering," to "their camping ground," and finally to "the language used there." The sense shift then passes through itinerant merchants:
Hawkers use a special vocabulary and a special intonation when advertising their wares (think of modern auctioneers), and many disparaging, derisive names characterize their speech; charlatan and quack are among them.
[Slang] is a dialectal word that reached London from the north and for a long time retained the traces of its low origin. The route was from "territory; turf" to "those who advertise and sell their wares on such a territory," to "the patter used in advertising the wares," and to "vulgar language" (later to “any colorful, informal way of expression”).
[S]lang is a conscious offence against some conventional standard of propriety. A mere vulgarism is not slang, except when it is purposely adopted, and acquires an artificial currency, among some class of persons to whom it is not native. The other distinctive feature of slang is that it is neither part of the ordinary language, nor an attempt to supply its deficiencies. The slang word is a deliberate substitute for a word of the vernacular, just as the characters of a cipher are substitutes for the letters of the alphabet, or as a nickname is a substitute for a personal name. [Henry Bradley, from "Slang," in Encyclopedia Britannica, 11th ed.]
A word that ought to have survived is slangwhanger (1807, American English) "noisy or abusive talker or writer."
late Old English scoru "twenty," from Old Norse skor "mark, notch, incision; a rift in rock," also, in Icelandic, "twenty," from Proto-Germanic *skur-, from PIE root *sker- (1) "to cut."
The notion probably is of counting large numbers (of a passing flock of sheep, etc.) by making a notch in a stick for each 20. The prehistoric sense of the Germanic word, then, likely was "straight mark like a scratch, line drawn by a sharp instrument." That way of counting, called vigesimalism, is widespread and also exists in France and left its trace in the language: In Old French, "twenty" (vint) or a multiple of it could be used as a base, as in vint et doze ("32"), dous vinz et diz ("50"). Vigesimalism was or is a feature of Welsh, Irish, Gaelic and Breton (as well as non-IE Basque), and it is speculated that the English and the French learned it from the Celts. Compare tally (n.).
By early 13c. it is attested in the sense of "a financial record" (perhaps one kept by tallies), and it is attested from early 14c. as "reckoning, total amount." The specific sense of "a reckoning or account kept by means of tallies" is clearly attested by c. 1400, especially (1590s) "mark made (by chalk, on a taproom door, etc.) to keep count of a customer's drinks."
This was extended by c. 1600 to "amount due, one's debt," and by 1670s to "mark made for purpose of recording a point in a game or match," and thus "aggregate of points made by contestants in certain games and matches" (1742, in whist).
The sporting score-card is by 1877 (in cricket). The newspaper sports section score line is by 1965. Score-keeping in sports is by 1905. From the tavern-keeping sense comes the meaning "amount on an innkeeper's bill" (c. 1600) and thus the figurative verbal expression settle scores (1775; as cut scores, 1610s).
Meaning "printed piece of music" is recorded by 1701, said to be from the practice of connecting related staves by scores (in the "line drawn" sense). Especially "music composed for a film" (1927). In underworld slang, "money obtained in a crime," 1914. Meaning "an act of obtaining narcotic drugs" is by 1951.
The meaning "a cut, notch, scratch or line made by a sharp instrument," without reference to counting, is attested from c. 1400. By c. 1600 as "a line drawn."