snow-plow n.

Middle English snou, from Old English snaw "snow, that which falls as snow; a fall of snow; a snowstorm," from Proto-Germanic *snaiwaz (source also of Old Saxon and Old High German sneo, Old Frisian and Middle Low German sne, Middle Dutch snee, Dutch sneeuw, German Schnee, Old Norse snjor, Gothic snaiws "snow"), from PIE root *sniegwh- "snow; to snow" (source also of Greek nipha, Latin nix (genitive nivis), Old Irish snechta, Irish sneachd, Welsh nyf, Lithuanian sniegas, Old Prussian snaygis, Old Church Slavonic snegu, Russian snieg', Slovak sneh "snow"). The cognate in Sanskrit, snihyati, came to mean "he gets wet."

As slang for "cocaine" it is attested from 1914.

"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.