Green’s Dictionary of Slang

bahakas n.

also bahook(e)y
[ety. unknown]

buttocks, behind.

[US]S. Morgan Homeboy 4: Squares gave Rings ’n’ Things a pain in the bahakas.
[UK]I. Rankin Black Book (2000) 133: Jock would recognise a racehorse’s bahookey quicker than a human face.
[UK]I. Rankin Falls 420: He happened to glance in his rearview and caught the cop car up his bahooky.
[UK](con. 1980s) I. Welsh Skagboys 214: The idea of Simon’ big, fat cock up ma bahookay makes me feel queasy.