sound of impact, attested from 1952, echoic.
thunk (v.)
dialectal or jocular past tense or past participle of think, by 1876. Not historical, but by analogy of drink/drunk, sink/sunk, etc.
the basketball made a thunk as it hit the rim
thunderclap
thunderhead
thunderous
thunderstorm
thunderstruck
thunk
Thuringia
Thursday
thus
thusly
thwack
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