Yep, now I remember - Vasusena was what Karna was named. Incidentally, he was called Karna long before he sacrificed the kavach/kundal, which was sometime before the war, when it looked inevitable that he wouldn't abandon the Kauravas. Like at the archery contest where he humiliated Arjun, Karna was what he was called.
True. But what I was referring to was this:
First he was Vasusena.
Because he hewed his armouroff his body he became
Karna the Cutter.From Adi Parva > Sambhava Parva, Section 111, Sloka 42. (P. Lal Transcreation)