It’s an Italian slang term to close a deal The Sicilian style. To kill everyone involved, preferably with a knife but in a pinch a gun will suffice. To kill them all

n. The birth name of somebody who has changed their name. Most commonly attributed to trans people, but can be attributed to any person who has changed their name. (sometimes written as two words: dead name)

v. 1. To call somebody by their deadname.
v. 2. To out somebody's deadname to the public.