Biscuit, Grog, Grasshopper, Kwan, FP, and Razor of course. The stories are varied and cover more than three decades so I won't trouble you with too much detail.
Biscuit was a gift from my brother referring to the back of my head after a very short hair cut one time. He said the back of my head looked like... you guessed it.
Grog was back in the Tim Allen days when every guy was grunting like a caveman. A couple of friends and I were all given cavemen names. Don't know why. I was a sensitive, understanding, feeling kind of guy back then...yea, well, kind of, lol.
Grasshopper, Kwan, and Razor(foot) are all MA related from people I trained with or who knew I trained.
And my personal favorite, FP, came from some one near and dear to my heart who still calls me that to this day but only when I get a bit too sarcastic, lol.