I've just discovered this question on Quora: What is the story behind your username at CodeForces?. I guess it'd be pretty interesting to hear stories from top participants. For instance, my handle's history is already described there.
This blog is dedicated to everyone who don't have Quora account, so you can share your histories and comments here.
I personally would love to hear stories from tourist, rng_58 and YuukaKazami from current top-10.