Green’s Dictionary of Slang

gab v.

[gab n.1 ; considered SE by the OED, but used in many sl. combs. below and thus included here]

[late 14C+] to talk.

In derivatives

gabfest (n.) (also gab session) [-fest sfx] [late 19C+] (orig. US)

1. a gathering for talk; a spell of talking; a prolonged conference or conversation.

2. garrulous, unrestrained talk.

gabster (n.) [-ster sfx]

[19C] a chatterer, an idle talker.

In compounds

gab-artist (n.) [-artist sfx]

[20C+] (US) a talker, esp. a convincing talker.

gab-bag (n.) [SE bag/-bag sfx]

[1940s] (Aus.) a gossip.

gabslick (n.) [slick n.1 (2)]

[20C+] (Ulster) a talkative person.

In phrases