Young Fireman Recruits, Fireman Apprentices or Fireman ( Fireman was designation for E 1 through E 3 who worked in the engineering spaces) would be sent to the Boiler Room to get a BT punch ( BT = Boiler Technician). Came back with a sore arm from the BT punch.
Fireman didn't specifically refer to a firefighter. Everyone on board was considered a firefighter, Admiral on down. When your house is on fire in the middle of the ocean it's taken rather seriously. The thought of a fire on the sub was really taken seriously, especially when submerged.