Green’s Dictionary of Slang

gagger n.1

[gag v.]

1. [late 18C–early 19C] a confidence trickster, a cheat, esp. when telling ‘sob-stories’ or posing as a deaf-mute.

2. [mid-19C–1910s] a joker; in theatrical context, esp. of comedians, one who ad-libs.

3. [late 19C-1930s] a tramp, a beggar, who uses ’true’ stories to enhance the basic beggar’s entreaties.

4. [1940s] (US Und.) a receiver of stolen goods.

5. [1940s] (US tramp) a tramp who makes a living by telling stories.