Origin of thwackprobably echoic
transitive verbthwacked, thwack·ing, thwacks
Origin of thwackImitative
(third-person singular simple present thwacks, present participle thwacking, simple past and past participle thwacked)
From a variant (influenced by whack) of Middle English thakken (“to stroke"), from Old English Ã¾accian (“to touch gently, stroke, tap"), from Proto-Germanic *Ã¾akwÅnÄ… (“to touch lightly"), from Proto-Indo-European *tag-, *taÇµ- (“to touch"). Cognate with Old Dutch Ã¾akolÅn (“to stroke"), Old Norse Ã¾ykkr (“a thwack, thump, blow"), Icelandic Ã¾jÃ¶kka, Ã¾jaka (“to thwack, thump, beat"), Norwegian tjÃ¥ka (“to strike, beat"), Latin tangÅ (“touch"). More at tangent.