Green’s Dictionary of Slang

1. a fool; a layabout.

1971		AS XLVI 300: [Yiddish words in English], Doppes [...] blockhead, slob.
1981		in Peers & Bennett 1,001 Logical Laws 113: A doppess is always dropping things, but a sclemiel picks up after him.

2. an ineffectual observer who in a crisis offers no practical help, merely sympathetic banalities.

1968		L. Rosten Joys of Yiddish 100: Doppess-Pronounced dop-pess, to rhyme with ‘mop-less.’ Not Hebrew but Ameridish: a local coinage of the garment center in New York. Useless but commiserating bystander; ineffectual observer who is of little help [...] Doppess [...] a character type known in all cultures: the useless observer who, in a crisis, does nothing more than offer obligatory sympathy.
2001		Forward (N.Y.) 30 Mar. n.p.: The word [...] has even merited a definition by the eminent sociologist Daniel Bell that distinguishes it from ‘shlemiel,’ viz.: ’The shlemiel is the pants presser who always drops the hot iron off the ironing board. The shlimazl is the shmo on whose foot the iron always falls. And the doppess is the one who says, “Tsk! Tsk!”’.