Green’s Dictionary of Slang

1. to hit.

1918		M. Doolittle Outlook Nov. 433: Heads may be biffed or bammed or bumped [W&F].
1920		Ade Hand-made Fables 146: He had applauded when vicious Pugs bammed each other in a padded Ring.
1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 64: Come on Studs! Bam him!
1965		H. Williamson Hustler 191: She just turned right around, bammed the register, and handed me the money!

2. in fig. use of sense 1, to have sexual intercourse.

1970

‘Troy Conway’ Cunning Linguist (1973) 145: Failing all else, I would get both my broads deliriously swacked and bammed and banged on what I now consider Magda’s Ploy. Another wonderful way to travel in a boudoir.