Old English recan (Anglian), reocan (West Saxon) "emit smoke," from Proto-Germanic *reukanan (cf. Old Frisian reka "smoke," Middle Dutch roken, Dutch rieken "to smoke," Old High German riohhan "to smoke, steam," German rauchen "to smoke," riechen "to smell").
Originally a strong verb, with past tense reac, past participle gereocen, but occasionally showing weak conjugation in Old English. Meaning "to emit smoke;" meaning "to emit a bad smell" is recorded from 1710 via sense "be heated and perspiring" (early 15c.). Related: Reeked; reeking.