Probably from a dialectal variant of snithe (“sharp, cutting, cold”). See snithe (adjective).
Alternatively, possibly a metathetic corruption of Middle English snythand (“piercing (the heart), cold, biting”, literally and figuratively). More at snithe (verb).
Compare typologically cutting, Russian ко́лкий (kólkij) (akin to коло́ть (kolótʹ)).