thwartyoudaoicibaDictYouDict[thwart 词源字典]
thwart: [13] Thwart was originally an adverb and adjective, meaning ‘across, crosswise’. It was however used as a verb, meaning ‘obstruct’ (from the metaphorical notion of ‘crossing’ someone) as early as the 13th century. It was borrowed from Old Norse thvert, the neuter form of thverr ‘transverse’. This went back to a prehistoric Germanic *thwerkhwaz (possible source also of English queer), which in turn was descended from Indo-European *twork-, *twerk- ‘twist’ (source also of English torch, torment, torture, etc).

How the noun thwart ‘seat across a boat’ [18] fits into the picture is not altogether clear. Its modern meaning clearly connects it with thwart ‘across’, but the notion of ‘crosswise’ may have been a secondary development. For an earlier noun thought ‘seat in a boat’ existed, which came ultimately from Old English thofta ‘rower’s bench’, and it could be that thwart the modern English noun represents a blending, both formal and semantic, of thwart ‘across’ with the now obsolete thought.

=> queer, torch, torment, torture[thwart etymology, thwart origin, 英语词源]
thwart (adv.)youdaoicibaDictYouDict
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" (cognates: 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 *terkw- "to twist" (cognates: Latin torquere "to twist," Sanskrit tarkuh "spindle," Old Church Slavonic traku "band, girdle," Old High German drahsil "turner," German drechseln "to turn on a lathe"), possibly a variant of *twerk- "to cut." From mid-13c. as an adjective.
thwart (v.)youdaoicibaDictYouDict
"oppose, hinder," mid-13c., from thwart (adv.). Related: Thwarted; thwarting.