Green’s Dictionary of Slang

tommy gun n.

also Tommy, tommy, Tommy gun
[one of the earliest brands, the .45 calibre Thomson]

(orig. US Und.) a sub-machine gun; also attrib.

[US]Sat. Eve. Post 13 Apr. 54/3: There are three types of machine guns used — Tommy guns, Browny guns and Louie guns [DA].
[US]R. Whitfield ‘About Kid Deth’ in Penzler Pulp Fiction (2007) 278: Bess had screamed [...] And then the Tommy had been turned loose.
[US]J. Spenser Limey 27: There was a Thompson sub-machine gun, universally known in gangland as a ‘Tommy-gun.’.
[US]Mezzrow & Wolfe Really the Blues 63: Their cute little Ford tagged along behind those big trucks [...] nobody ever guessing that it was loaded up with tommy guns.
[UK]P. Bowman Beach Red 57: One tap on the Tommy butt means halt.
[US]‘William Lee’ Junkie (1966) 13: One day he called me up and said he had stolen a Tommy gun.
[US]‘Blackie’ Audett Rap Sheet 115: We had split up with Johnny and he had taken his tommy with him.
[US]Mad mag. June 48: Whenever some rat / Starts to chat / Tommy answers ‘Rat-tat-tat.’.
[US]J. Charyn Once upon a Droshky 161: Joel is holding a plastic tommy gun.
[US](con. 1949) J.G. Dunne True Confessions (1979) 97: They’re coming in after you, like in the movies. The chief’s got a tommy gun, for Chrissake.
[Aus]Hackworth & Sherman About Face (1991) 147: Nomcombat types who wanted to play out the role of a tommy-gun-toting warrior.
[US](con. 1964–8) J. Ellroy Cold Six Thousand 208: They yanked guns. They dollied them over — full-drum Thompsons/one hundred plus [...] The troops stacked the Tommys. Pete ignored them.

In compounds

tommy man (n.)

(US Und.) an armed gangster.

[US]Hostetter & Beesley It’s a Racket! 240: tommy man — A machine or sub-machine gunner.
[US]G. Milburn ‘Convicts’ Jargon’ in AS VI:6 441: Tommy-man, n. A machine-gunner for a mob.