Green’s Dictionary of Slang

1. (US) incompetent.

1888

St Paul Daily Globe (MN) 23 May4/8: The opinion prevails here that the Chicagos [i.e. a baseball team] are chumpish.

2. foolish, stupid.

1890		Wichita Eagle (KS) 5 Jan. 8/2: We have no such chumpish lawyers as the one of whom the story is told in London.
1895		Eve. Star (Wash., DC) 16 Aug. 6/2: For ach chumpish youth [...] there is a maid to vow he is the smartest man on earth.
1906		S.F. Call 21 Oct. 31/1: It may be chumpish of me to say that for publication, but it’s the truth.
1933		M. Marshall Tramp-Royal on the Toby 266: Feeling chumpish all over, I sought the sidewalk.