Back in middle school years ago I played a 2d MMO called Tibia. I had a knight named "Knight Sefier." When I came to WoW I went through characters til I finally found the one I wanted, and named him "Sefier." After a few changes, I went from Sefier to Sef due to the nickname that everyone had for it.
Sefier came from the Final Fantasy 8 character, though it was spelled Seifer. I am guessing I just accidentally spelt it wrong back then and I stuck with it ever since. <3 it