Green’s Dictionary of Slang

an onomat. term indicating a loud noise or explosion.

1970		B. Oakley Salute to the Great McCarthy 196: Up like a rocket, down like a stone. kaboom. A write-off.
1973		S. Ace Stand On It (1979) 154: He [...] let it slide right into the wall. Ka-boom!
1981		S. Berkoff Decadence in Decadence and Other Plays (1985) 22: A minute atomic bomb [...] ka boom ka blast ke pling!
1994		G. Disher Crosskill [ebook] Maybe wire it [i.e. a bomb] to the telephone, ring the house and kaboom.
1999		Guardian Guide 6–12 Nov. 6: Do you feel lucky? Well do you, you slag ponce?’ KA-BOOM!!!
2007–8		Mail and Guardian (S. Afr.) 21 Dec.–3 Jan. 48: [cartoon] Three ATM’s – Ka-Boom!