In the US Navy at least, you don't "fire" a torpedo, you "shoot" it. The lore is that "fire" has a very specific, very urgent meaning on a warship and you don't use that word unless there actually is a fire.
There are lots of these hyper-specific "reserved keywords" in the military. Another one from the US Army is "repeat", which is the command for an artillery battery to fire again with the same parameters as their previous barrage. Therefore on the radio we only ever used "say again" to ask someone to repeat their last transmission. Even if no one on the radio had ever or would ever be involved in artillery operations, I imagine it's easier to just train the entire force on a single uniform standard.