Old English þawian (transitive), from Proto-Germanic *thawon- (source also of Old Norse þeyja, Middle Low German doien, Dutch dooien, Old High German douwen, German tauen "to thaw"), from PIE root *ta- "to melt, dissolve" (source also of Sanskrit toyam "water," Ossetic thayun "to thaw," Welsh tawadd "molten," Doric Greek takein "to melt, waste, be consumed," Old Irish tam "pestilence," Latin tabes "a melting, wasting away, putrefaction," Old Church Slavonic tajati "to melt"). Intransitive sense from early 14c. Related: Thawed; thawing.