I think it was in 2007 on the PCT. A guy gave himself a cool sounding trailname on his trail journal because he wrote, "I don't want to get a trailname like Pink Gumby". When I read that, I thought "FOOL, you just named yourself the name you didn't want." Sure enough that's what hikers started calling him since hikers read other journals before they start hiking.
When I hiked the PCT, there was a girl who resisted every name thrown at her because she wanted a one with a good story behind it. She finally got hers near the Calf-Oregon border after mailing her sleeping bag ahead during a heat wave (bad idea) and then the temperature dropped and she was desperately using a borrowed e-blanket to stay warm at night. Another guy I hiked with, real name was Miles. He didn't get his trail name until almost Washington because most of us thought Miles was his trail name.
Trail names can be fun. They can also be a bit mean spirited in some cases (choose your hiking partners carefully). Most thru-hikers know each others trail names but have no clue what their real names are, even if they hiked with someone for months.
-Miner (there is a story there about an ice-axe digging a cathole, and a trail that looped around the out of the way tree that I thought was off trail).