clobber · verb, noun1
British slang from 1941; possibly onomatopoeic of the sound of detonated bombs in the distance.
clobber · noun2
British slang from 19th century of unknown origin, perhaps from Yiddish.
clobber · noun3
Of obscure origin, but compare clabber (“mud, wet clay”).
Etymology from Wiktionary, CC BY-SA 4.0.