Green’s Dictionary of Slang

(Can., mainly west coast) satisfactory, OK.

1881		Montana Standard (Butte, MT) 19 July 3/3: J.K. Pardee is [...] reporting that flourishing camp in ‘skookum’ condition.
1896		Scranton Republican (PA) 22 Jan. 6/2: The Siwash [...] language is realy wonderful [...] if anything is good, it is ‘skookum’.
1906		S. Ford Shorty McCabe 138: When it comes to doing the hair-trigger friendship act, Pinckney’s the real skookum preferred.
1916		P. Kyne Cappy Ricks 77: I’ll bet he’s going to make a skookum skipper.
1922		P.A. Rollins Cowboy 78: A few words were borrowed from the Chinook jargon of the coastal trappers and traders. The words most commonly taken [...] were ‘skookum’ (great), ‘siwash’ (an Indian).
1936		R.F. Adams Cowboy Lingo 205: A few words were borrowed from the Chinook jargon [...]. ‘Skookum,’ meaning great.
1949		Sierra Club Bulletin June 105: Billy and Pete were skookum, and I was pretty good myself in those days [DA].