Egregoros

I think fantasy RPGs misattributed the name because in real life the bastard sword is indeed a sword that is actually shorter in blade length than a standard longsword but has a handle just long enough to allow you to grip it two handed or in one hand.

but to be fair, the “bastard sword” classification is a modern thing and the more historical name for a short longsword would be a ”hand and a half sword”