Green’s Dictionary of Slang

from the authority’s point of view, suspicious; thus suspishly adv.

1882		Graphic (London) 15 Apr. 1/1: [picture caption] ‘This village is suspish.’ ‘Confound it, how do they known I’m English’.
1915		Bucks Examiner 5 Mar. 5/5: I do not say it is done for the purpose, only it looks very ‘suspish’.
1923		Abbeville Meridional (LS) 29 Sept. 3/7: ‘Some tam Labelle she is look lak she is make some love with Soke Smith. Pon Pon is commance fu look suspish’.
1943		J. Phelan Letters from the Big House 32: The screws was gettin’ suspish.
1950		Chicago Trib. 19 July 18/5: Of frozen fish / I’m suspish.
1954		J. Phelan Tramp at Anchor 145: I was ‘out exceptional early, and a bit suspish, so they took no chances’.
1985		T.R. Houser Central Sl. 50: suspishly, actin [...] ‘Boys on the side of the house been actin’ suspishly.’.