thwart (adv.)
late 14c.,
thwert, "from side to side, across, transversely; crosswise, across the grain," earlier in the same sense
thwertover (c. 1200),
overthwert (c. 1300), from a Scandinavian source, probably Old Norse
þvert "across," originally neuter of
thverr (adj.) "transverse, across," from Proto-Germanic
*thwerh- "twisted, oblique," which according to Watkins is from PIE root
*terkw- "to twist."
It is thus cognate with Old English
þweorh "transverse, perverse, angry, cross," and the Proto-Germanic word also is the source of Middle Dutch
dwers, Dutch
dwars "cross-grained, contrary," Old High German
twerh, German
quer, Gothic
þwairhs "angry."
The spelling shifted to
-a- from 15c. From mid-13c. as an adjective, "contrary, stubborn, obstinate;" earlier
overthwert,
thwertover "blatant, outright" (c. 1200). As a preposition from early 15c., "across, athwart, from one side to the other."
thwart (v.)
mid-13c.,
thwerten, "oppose, hinder, run counter to," from
thwart (adv.). Later in a physical sense of "lie across the course of, extend across, lie across so as to interrupt" (mid-14c.), also of the eyes,
thwarting, "glancing sideways, looking askance." From early 15c. as "pass over or across." Spelling change from 15c. Related:
Thwarted;
thwarting.