Green’s Dictionary of Slang

1. (US Und.) aware, in the know.

1907		News & Courier (Charleston, SC) 14 Apr. 18/1: These hair harvesters down here sure are Jakey Next to all the new stuff.
1916		Seattle Star 11 Nov. 8/3: Key to Broadway Slang! [...] He fanned me like I was a Wilbur, but I was Jake to his play; he thought I might try to work a crash.

2. (Aus./N.Z./US) satisfactory, as required; esp. in phr. she’s/she’ll be/we’re jake, it’s fine, things will be fine, we are fine.

1914		Jackson & Hellyer Vocab. Criminal Sl. 48: As an adjective ‘jake’ means good; satisfactory; acceptable; all-right.
1918		Aussie (France) VIII Oct. 9/1: Mad: ‘But, Monsieur, how will you make soup from water only?’ / Shroo: ‘She’s jake, Madame. This is the way they make it in Aussie.’.
1918		Cairns Post 12 Mar. 7/4: The British Recruiting Mission have prepared a glossary of trench slang [...] Jake - universal army term to express satisfaction.
1927		Smith’s Wkly (Sydney) 20 Aug. 11/2: Eventually the model ‘S.M. Herald’ leader will read like this [...] Some one will go ’im scone ’ot and then it’ll be ’im for the tall timber. That’s jake.
1929		W.R. Burnett Little Caesar (1932) 18: ‘Everything’s jake,’ said Scabby.
1932		Townsville Daily Bull. 8 July 5/3: The suit was jake, an’ made me look like a respectable citizen.
1939		R. Chandler Big Sleep 114: Just keep your nose clean and everything will be jake.
1944		L. Glassop We Were the Rats 5: It’s oke. Everythin’s jake.
1951		D. Stivens Jimmy Brockett 103: When there were enough people in Parliament who wanted to do Jimmy Brockett a good turn, I’d be jake.
1953		R. Chandler Long Good-Bye 53: I’m offering you a chance to clear yourself. If you don’t want it, that’s jake with me too.
1961		R.S. Close With Hooves of Brass 125: If he could catch her attention, and she waved in reply, then he would know things were going pretty jake.
1962		R. Cook Crust on its Uppers 71: He just bends down very deep [...] which means everything’s jake.
1976		R. Morrieson Pallet on the Floor 115: If we hang on for a month or two we’ll be jake.
1984		W. Ammon et al. Working Lives 109: She’ll be jake. No worries.
1999		G. Seal Lingo 98: Condemnation of Australian casualness expressed in phrases like she’ll be jake, she’s apples and no worries, is nothing new.
2006		F.X. Toole Pound for Pound 220: Everything’s jake around here.