Why is it called Bastard Sword?

When created it basically never really fit in to any family of sWords, like the wakizashi fits in with the katana, or kunai fitting in with shuriken, things of that sort. Therefore, it never really had a family of sWords and was not improved from another sWord, therefore no "father" to this blade. Thus the name.

The bastard sWord gave origin to the longsWord also known as a "hand and a half" sWord. The name "bastard sWord" has its own explanation rooted in the French epee batarde. This term was born of confusion over how to categorize the weapon.