Enlarge Person :: d20srd.org
Though the weapon is enlarged too, IMO it's not conclusive whether this also counts for the weapon class. I wonder if you can use the feedback thingy in NWN2 to figure this one out, provided you enable it to show everything.
It would be so much easier if these things were just regular skills like Parry or Tumble. I don't even particularly understand why a larger person or weapon should have an easier time disarming. It seems more like a finesse/intelligence thing. But whatever.