Wouldn't "gas filler lock" be a bit more descriptive?
Hmm...
'gas' - that would be gasoline, petrol, engine fuel, I get that.
'filler' - that which fills - That would be the station pump, the pump hose, the pump handle, maybe even the pump operator. Nope, nothing attached to my C14 fills the tank, I have to do that myself. However, whenever I do so, I have to unlock and uncover a large round
'hole' to put the nozzle in to. So I guess "gas filler" is NOT more descriptive, IMHO.