Green’s Dictionary of Slang

1. (US campus) to depart, to go away; to leave someone in peace; also as imper.

1957		M. Shulman Rally Round the Flag, Boys! (1959) 54: Oh, flake off, little man!
1964		in Current Sl. (1967) I:4 4/1: Flake off, v. Leave [...] An imperative ‘Leave me alone.’.
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 15: flake off – Get lost!
1971–2		C. Shafer ‘Catheads [...] and Cho-Cho Sticks’ in Abernethy Bounty of Texas (1990) 204: ‘Flake off!’ v. – a rude way of asking someone to leave.
1972		(con. 1950s) Jacobs & Casey Grease II iv: Why don’t you guys just flake off and leave me alone?
1979		S. King Long Walk in Bachman Books (1995) 272: Now what say you flake off?

2. (US campus) to irritate; to act irritatingly.

1969		Current Sl. III:3 6: Flake . . . off, v. To annoy.
2001		C. Stella Eddie’s World 4: Diane, when she isn’t flaking off about some new Internet gimmick, she wants a kid.

3. (US black) to break off one’s line of thought.

1971

H.E. Roberts Third Ear n.p.: flake off v. 1. to break away from line of thought; e.g. She flaked off in the middle of our talk. 2. When used in the imperative, ‘flake off!’ means ‘get out’.

4. (US, also flake) to back down in an argument or fight.

1990		N.Y. Mag. 28 May 27/1: [black high school slang] ‘Flakin’’ [...] backing down.
1993		Lerner et al. Dict. of Today’s Words.