thwart / [unvoicedth]wôrt/ • v. [tr.] prevent (someone) from accomplishing something: he never did anything to thwart his father he was thwarted in his desire to punish Uncle Fred. ∎  oppose (a plan, attempt, or ambition) successfully: the government had been able to thwart all attempts by opposition leaders to form new parties.• n. a structural crosspiece sometimes forming a seat for a rower in a boat.• prep. & adv. archaic or poetic/lit. from one side to another side of; across: [as prep.] a pink-tinged cloud spread thwart the shore.

thwart1 (arch.) adv. and prep. athwart XII (first in þwert ut thoroughly); adj. obstinate, perverse XIII. ME. þwert — ON. þvert, orig. n. of þverr transverse, cross = OE. þwe(o)rh crooked, cross, perverse, OHG. dwerh, G. zwerch, Goth. þwairhs cross, angry :- Gmc. *þwerχwaz, f. IE. *twerk- *twork-, as in L. torquēre twist.
Hence thwart vb. †oppose XIII; †extend from side to side of XV; †place crosswise XVI; foil, frustrate.

thwart2 rower's bench. XVIII. var. (presumably after THWART1) of thought, which is evidenced from XIV as a var. of earlier dial. thoft, OE. þofte = MDu. dofte, dochte (Du. doft), OHG. dofta, ON. þopta :- Gmc. *tuftō; the history is obscure.