"agricultural implement drawn by animals, used to cut ground and turn it up to prepare it for sowing or planting," late Old English ploʒ, ploh "plow; plowland" (a measure of land equal to what a yoke of oxen could plow in a day); in reference to the implement perhaps from a Scandinavian cognate (such as Old Norse plogr "plow;" compare Swedish and Danish plog; Middle English Compendium notes that, "As an element in names, plough is most freq. in the area of the Danelaw"); from Proto-Germanic *plōga- (source also of Old Saxon plog, Old Frisian ploch "plow," Middle Low German ploch, Middle Dutch ploech, Dutch ploeg, Old High German pfluog, German Pflug), a late word in Germanic, of uncertain origin.
Rare as a word alone in Old English, where the usual word for "plow" (n.) was sulh (later sull), which is cognate with Latin sulcus "furrow" (see sulcus).
Old Church Slavonic plugu, Lithuanian plūgas "plow" are Germanic loan-words, as probably is Latin plovus, plovum "plow," a word said by Pliny to be of Rhaetian origin. Boutkan argues against that and points out that, "A priori, the initial p- [in a Germanic word] points to a probable non-IE origin." He also notes the unclear etymological connection with Albanian plúar "plow," which "may have the same, apparently Central-European origin as the Gmc. etymon. On the other hand, the word may represent a North-European innovation which would also be found in OIr. dlongid 'split' < *tlong-." For the usual IE "plow" word, see arable.
The plow and the use of it would have been familiar to most people in England (and later America) from remote antiquity to fairly recent times, and it thus figures largely in image and metaphor; Middle English had (modernized) govern the plow of battles "command an army, wage war;" drive (or hold) the plow "bear burdens; gain the authority;" have weak oxen in the plow "not have energy for the undertaking;" put (one) in pain's plow "force to suffer;" and slightly later plow the sand "labor fruitlessly."
As a name for the star pattern also known as the Big Dipper or Charles's Wain, it is attested by early 15c., perhaps early 14c., also Arthouris Plowe. The three "handle" stars (in the Dipper configuration) generally are seen as the team of oxen pulling the plow, though sometimes they are the plow's handle.
1756, "special vocabulary of tramps or thieves" or any set of persons of low character, 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.
Liberman concludes:
[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”).
The association of the word with thieves and low life faded in the 19c.
[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.]
