dunhead, n. — Green’s Dictionary of Slang

dunhead n.

also dunghead

[? colloq. dunderhead, but note dunny n.² (2), i.e. synon. with shithead n. (1)]

(Aus.) a general term of abuse.

1955		D. Niland Shiralee 63: Only for you taking care of that dunhead [...] it might have been a different story.
1976		J. Stanley World War III (1979) 48: ‘You dunghead,’ interjected Chi-yung, the sergeant.