I got the "weapon knife" from Dr. David C. Fowler, a ballad scholar who taught a course in "The Popular Ballad" at the University of Washington. I can't recall what they were offhand, but he had a couple of fairly authoritative sources for that (which is to say, he didn't make it up), so I don't think it's "fanciful modern nonsense."

"Nut brown" or "brown sword" is one that throws me. I don't recall ever hearing it, and I haven't found anything in the arms and armor books to give me a clue, but I'll keep looking.

Don Firth