Green’s Dictionary of Slang

1. the end result, the final assessment.

1976		R. Daley To Kill a Cop 212: ‘[I]t still leaves us short of the bottom line. The bottom line, I’m afraid, is that probable cause would not be sufficiently alleged’.
1988		D. Woodrell Muscle for the Wing 186: The bottom line is, all these punks have got to go.
1998		Source Oct. 224: Bottom line, however, nobody smacked sawed-offs to our collective mugs.
2001		Source Aug. 32: Bottom line is, you gotta live this shit to be this shit.
2010		A. Steinberg Running the Books 17: Bottom line [...] this cocksucker didn’t stab you in the throat, right?
1985		T. Wolff ‘Our Story Begins’ in Back in the World 172: ‘So what was the bottom line?’ Truman asked. ‘Simplicity itself,’ George said. ‘If Miguel messed up, they’d throw him on the first plane to Manila’.

2. something steady, reliable.

1997

L. Davies Candy 104: Candy was the steady income, the bottom line, and I was on special projects.