Green’s Dictionary of Slang

1. (also come on to) to approach sexually.

1937		R. Westerby Wide Boys Never Work (1938) 149: If you make a dead-line at six inches above the knees they always want to come on.
1956		N. Algren Walk on the Wild Side 174: Do you know about elephants, how they come on?
1958		E. Gilbert Vice Trap 30: She didn’t come on to [...] didn’t kiss me back.
1977		C. McFadden Serial 56: If I wore my tap-dancing shorts, Carol might think I was coming on.
1978		R. Price Ladies’ Man (1985) 228: When we were up in your crib Thursday night, it seemed like you were coming on to me.
1981		A.K. Shulman On the Stroll 35: She’d seen him [...] coming on to her French teacher, embarrassing her at school.
1996		P. Temple Bad Debts (2012) [ebook] She probably had a good laugh at being come on to by the likes of me.
2000		P. Howard Miseducation of Ross O’Carroll-Kelly (2004) 41: I told you before, she came on to me.
2000		W. Shaw Westsiders 313: Did you see that girl in the bodysuit? She was fucking coming on.
2002		C. Stella Jimmy Bench-Press 67: She came on to me. I fucked her.

2. (US) to joke.

1964

D. Stagg Glory Jumpers (1976) 64: What? Jump in France? Man, you’re coming on.