Green’s Dictionary of Slang

dodunk n.

[? dodo n. (1) + bohunk n. (2)]

(US) a fool, a simpleton.

1894
19001910
1915
[US]DN I 387: Dodunk, n. A stupid, simple person.
[US]M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 203: dodunk, a stupid, simple person. ‘Lloyd was the biggest dodunk I ever knew.’.