Green’s Dictionary of Slang

1. to make sexual advances towards, thus comeatable, susceptible to advances.

1779		Nocturnal Revels 2 72: She soon became a come-at-able piece at Haddock’s, and the rest of the Bagnios about the Garden [...] 2 141: [He] roamed at large amongst all the come-at-able Beauties and Demireps within the Bills of Mortality.
1838		Crim.-Con. Gaz. 10/1: From [...] the general tenor of her conduct, he flattered himself that she was come-at-able.
c.1850		Peeping Tom (London) 27 105/1: He flattered himself she was come-at-able.
1855		Broadway Belle (NY) 5 Mar. n.p.: By the way, is ‘Adele’ of Brooklyn, comeatable, say?

2. (Aus./N.Z.) to undertake, to take on, to get up to, to ‘try on’.

1901		Bulletin (Sydney) 28 Sept. 14/2: But, when for the fourteenth time he ‘came’ / At a bottle of unknown brand, / A long, lean drover proposed a game / And offered to take a hand.
1919		W.H. Downing Digger Dialects 17: come at (vb.) — Undertake.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: come-at. Undertake.
1959		(con. 1940s) G. Slatter Gun in My Hand 66: What the bloody hell ya comin at he said. [Ibid.] 212: Here, Sefton. What are you coming at?
1974		D. Ireland Burn 141: Don’t apologize to him. What are you coming at, Kincaid?
1999		G. Seal Lingo 61: The still-current term to come at something originated in World War I. Now, as then, it means to take on something, to join in, to agree.
2003		McGill Reed Dict. of N.Z. Sl. 50: come at To attempt, often used negatively, as in ‘Don’t come at that with me, mate, or I’ll drop ya.’ Mid C20.