As a fellow Norwegian now living in the UK: That term is so archaic and unusual in English that odds are quite a few people won't know it at all (In 24 years in the UK I don't think I've ever heard it used)

For the non-Norwegians: "Torpedo" in Norwegian has adopted the 1920s US slang for a hit man / hired gun, and in Norwegian it's in common, contemporary use, though more often for threats and violence than outright murder.