O.E., "fourth season of the year," from P.Gmc. *wentruz (cf. O.Fris., Du. winter, O.S., O.H.G. wintar, Ger. winter, Dan., Swed. vinter, Goth. wintrus, O.N. vetr "winter"), possibly from PIE *wed-/*wod-/*ud- "wet" (see water), or from *wind- "white" (cf. Celt. vindo- "white").
The Anglo-Saxons counted years in "winters," cf. O.E. ænetre "one-year-old." O.N. Vetrardag, first day of winter, was the Saturday that fell between Oct. 10 and 16. The verb meaning "to pass the winter (in some place)" is recorded from 1382. Winterize is from 1938, on model of earlier summerize (1935). Wintergreen as a type of plant is recorded from 1548.