Green’s Dictionary of Slang

short con n.

also short coin, short con game, short con racket, short money racket
[abbr. SE short (time) + con n.1 (7)]

1. [1930s+] (US Und.) any variety of confidence trick that can be performed spontaneously and on the spot, with no elaborate props, preparation etc.

2. attrib. use of sense 1.

In compounds

short con artist (n.) (also short con man, short con worker) [-artist sfx]

[1920s–50s] (US Und.) a confidence trickster who specializes in spontaneous or short-term trickery.