Green’s Dictionary of Slang

(US Und.) a thug, a hoodlum.

1920		C.E. Mulford J. Nelson xv 163: I’ve had all th’ visitin’ I want with a bunch of cold-deckers [DA].
1949		N. Algren Man with the Golden Arm 197: The old cold-deckers and the young torpedoes coming on faster than the law can pick them up.