c. 1200, from a Scandinavian source, probably Old Norse þvert "across," originally neuter of thverr (adj.) "transverse, across," cognate with Old English þweorh "transverse, perverse, angry, cross," from Proto-Germanic *thwerh- "twisted, oblique" (source also of Middle Dutch dwers, Dutch dwars "cross-grained, contrary," Old High German twerh, German quer, Gothic þwairhs "angry"), altered (by influence of *thwer- "to turn") from *therkh-, from PIE root *terkw- "to twist." From mid-13c. as an adjective.