gunsel
A gun-carrying hoodlum or other criminal.
There's somebody comin. I think it's that gunsel.
Where it comes from
By misunderstanding of the 1929 Maltese Falcon quotation above (1.1) (which survived in a popular 1941 film adaptation). The novel was originally serialized in a magazine, Black Mask, whose editor refused to allow vulgarities. Hammett used the word gunsel knowing that the editor would likely misunderstand it as relating to gun, and therefore allow it.
Adapted from the Wiktionary entry gunsel (CC BY-SA 4.0).