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.
c. 1300, from the noun, replacing Old English sniwan, which would have yielded modern snew (which existed as a parallel form until 17c. and, in Yorkshire, even later), from the root of snow (n.). The Old English verb is cognate with Middle Dutch sneuuwen, Dutch sneeuwen, Old Norse snjova, Swedish snöga.
Also þikke as snow þat snew,
Or al so hail þat stormes blew.
[Robert Mannyng of Brunne, transl. Wace's "Chronicle," c. 1330]
The figurative sense of "overwhelm; surround, cover, and imprison" (as deep snows can do to livestock) is 1880, American English, in phrase to snow (someone) under. Snow job "strong, persistent persuasion in a dubious cause" is World War II armed forces slang, probably from the same metaphoric image.