Green’s Dictionary of Slang

1. (orig. US) a murder; thus bump-off guy n., a killer.

1924		G. Henderson Keys to Crookdom 410: One who kills, croak artist, a blood, bump-off guy.
1929		C. Coe Hooch! 80: The D.A. played the game on that an’ satisfied the papers about nol-prossin’ that bump-off over in the East End? [Ibid.] 107: It wouldn’t mean so much as a headache to me to slip that bird the bump.
1931		C.S. Montanye ‘Tight Spot’ in Complete Stories 15 Sept. 🌐 I was just wondering what Killer Berg [...] will do about the bump off.
1939		R. Chandler Big Sleep 168: You know the dope on Brody’s bump-off.
1941		J.K. Butler ‘Saint in Silver’ in Goulart (1967) 96: He saw it was a good spot for a bump-off.
1943		R.L. Bellem ‘Dissolve Shot’ Dan Turner – Hollywood Detective May 🌐 If I solved the mystery of the threats I might also clear up the Belmont bump.
1950		Crime Smashers Oct. 26: [comic] Jeepers! It was a genuine bump-off.
1960		C. Cooper Jr Syndicate (1998) 9: Everything was lavish and class, nothing like those two-grand bumps.

2. attrib. use of sense 1.

1943

R.L. Bellem ‘Dead Man’s Shakedown’ in Dan Turner Detective Mar. 🌐 I’ll try to make sure you don’t get sucked into a bump-off mess.

3. the end of something, typically criminal activity.

1931

Irwin Amer. Tramp and Und. Sl. 42: bump off.- [...] the end of anything, usually of a criminal ‘job.’ .