thunk (n.)youdaoicibaDictYouDict[thunk 词源字典]
sound of impact, attested from 1952, echoic.[thunk etymology, thunk origin, 英语词源]
thunk (v.)youdaoicibaDictYouDict
dialectal or jocular past tense or past participle of think, by 1876. Not historical, but by analogy of drink/drunk, sink/sunk, etc.