Green’s Dictionary of Slang

bam n.⁴

a mindlesly violent, stupid person.

1993		I. Welsh Trainspotting 83: He kens thum aw through approved school, prison n the casuals networks, the freemasonries that bams share.
1996		A. Close Official and Doubtful 369: Those bams were lucky not to be taken for the IRA.
2012		(con. 1980s) I. Welsh Skagboys 41: YA FUCKIN WEE BAM! NEARLY FUCKIN WELL KILT US!
2015		I. Welsh Decent Ride 35: There’s bams whae outline the maist pointless, ludicrous jailbait propositions, jist usually cause thir lookin die a bit ay adventure.
2020		G. Armstrong Young Team 39: ‘He wis hettin weird.’ ‘Fair dos . . . looked like a bam’.

In derivatives

bammy (adj.)

stupid.

2012

(con. 1980s) I. Welsh Skagboys 273: You fuckin bam, Renton, you fuckin bammy simple dingul.