I usually use my environment or something that is related to my character. My main tag is usually some form of Autumnfire. That I just got because I love how trees look like they're on fire in the autumn. Also, kanji for Autumn is essentially Tree Fire. So it all kind of stuck for me and I've been using it for the past 15 years. But I don't always use it. Sometimes other names can be more appropriate if I have a character concept in mind. I once had a scythe wielding character who was pale and had white hair and had ghost like abilities, so her name was Geist. And once (man, this is soooo geeky, I can't believe I'm making this public) my sister translated my name into tolkien's version of elvish and I used that for a while.
But long story short, my inspiration comes from other languages, character concepts, and environment.
Main character: AutumEmber
60blm/whm Rank 7 Windurst