Here's info on the two swords I got from the Atari forum:
{4016}{Scather is a magic bastard sword that is both Chaotic and Holy. If the wielder is non-evil, Scather never misses and adds +4 to damage (doubles to +8 if the target is evil and the wielder is CN, CG, or NG. Finally, for CG wielders, Scather provides free unlimited Attacks of Opportunity against any opponent making a melee attack against the wearer (and CN wielders get one free such AoO per round).}
{4017}{Fragarach is a magic bastard sword that is both Chaotic and Holy. If the wielder is non-evil, Fragarach never misses and adds +4 to damage (doubles to +8 if the target is evil and the wielder is CN, CG, or NG. Finally, for CG wielders, Fragarach provides free unlimited Attacks of Opportunity against any opponent making a melee attack against the wearer (and CN wielders get one free such AoO per round).}
..which makes them the exact same sword, even though I had always been under the impression that Fragarach was supposed to be more powerful.
Go figure.
Edit: BTW, I checked them in-game, and both swords really are exactly the same, except Fragarch is gold and Scather is blue.