Green’s Dictionary of Slang

1. one who talks nonsense.

1914

R. Tressell Ragged Trousered Philanthropists (1955) 491: Not to mention such mental specialists as the holy reverend Belchers and Boshers.

2. (US Und.) an informer.

1903		H. Hapgood Autobiog. of a Thief 190: He certainly preferred to go to stir rather than have the name of being a belcher.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 25/2: Belcher. 1. The mouth. 2. An informer; one who turns State’s evidence. ‘The D. A. has a swag of (large number of) belchers stashed away (in protective custody) hollering murder (informing freely).’.
1957		El Paso Herald (TX) 3 Oct. 17/5: A few examples of [...] ‘calo’ [...] If the addict is caught via information furnished by infomers, the blame is rightfully affixed on ‘bat carriers’ or ‘belchers’.
1992		Bentley & Corbett Prison Sl. 36: Snitch also Rat An informant. […] (Archaic: crimp, shit-heel, buzz man, belcher).

3. a complainant.

1931		Irwin Amer. Tramp and Und. Sl. 25: Belcher.—A complainant or faultfinder. One who talks to excess. A prostitute who insists on explaining herself and her condition.
1933		Ersine Und. and Prison Sl.
1962		Ragen & Finston World’s Toughest Prison 790: belcher—A complainant or faultfinder.

4. (S.Afr.) a garrulous person.

1963

L.F. Freed Crime in S. Afr. 106: The word ‘belcher’ used by them signifies a talkative person.