Green’s Dictionary of Slang

bungo v.

[bungo n. but ? banjo v. (2)/bung v.1 (1)]

(US campus) to mistreat severely, to inflict injury on.

[US]Eble Campus Sl. Sept.
[US]Eble Sl. and Sociability 41: The verb bungo ‘seriously mistreat or inflict injury on’ is similar in both sound and meaning to bunk.