'bam' originates from imitative/onomatopoeic English, specifically the word 'bam', where the root meant 'a sudden loud sound' (an attempt to imitate the sound of impact).

'bam' has been used in English as an interjection and verb since at least the modern period as an onomatopoeic word; the verb formed regular past and past participle forms, producing 'bammed'.

Initially, it referred primarily to the sound itself ('a sudden loud noise'), but over time it also came to be used as a verb meaning 'to strike or cause such a noise', and adjectival usages derived from the verb (e.g. 'bammed' meaning dented or struck).