Green’s Dictionary of Slang

1. a chatterer; an indiscreet talkative person; a gossip.

[c.1386		Chaucer Persones Tale in Poetical Wks 148/1: He is a japer and a gabber, and not veray repentant].
1870		Cork Examiner 15 Nov. 3/4: More unprophetic weather for fighting could not be desired by the most inveterate gabber of the peace of society.
1893		Aberdeen Exp. 16 Oct. 4/8: ‘Where’s Mrs Gabber?’ [...] ‘Somebody told her an important secret and she has been out and about all day going from house to house visiting friends’.
1899		Bucks Herald 14 Oct. 3/1: Mrs Gabber (disdainfully): ‘He said there was no end to a woman’s tongue.’ — Mr Cynicus: ‘Which is certainly unture [...] because, if such were a fact, how in the world could it ever become sharp?’.
1939		W. Winchell On Broadway 4 Jan. [synd. col.] Mistinguette [...] has Paris gabbers frothing over her infatuation with young Carlos Machado.
1959		E. De Roo Go, Man, Go! 69: Some gabbers take all day to fold theirs.
1997		C. McPherson The Weir 47: She’s a gabber and a talker.

2. a lawyer.

1946

Charleston (WV) Daily Mail 2 Sept. 6/5: Me schmaltzy gabber couldn’t red a Chicago piano rap, so the D.A. conks me with a whole mag.

3. (US) a radio commentator.

1951		Green & Laurie Show Biz from Vaude to Video 568: Gabber – radio commentator.
2000		(con. 1940s–60s) Décharné Straight from the Fridge Dad 66: Gabber Radio commentator or D.J.

4. a police officer.

1989

J. Morton Lowspeak 63: Gabber – a policeman.