I made my username from something I'd been writing; I was intending to make a pony setting separate from mlp for a friend who, at the time, got tired of mlp for a while bc of interaction with the bad fans. I never finished building the setting beyond some species stuff and a creation myth that has a lot to do with a natural cycle of creation/destruction with the world. The being representing destruction was a dragon, so, when I was remaking a tumblr account and struggling with a username, I ended up thinking about that setting again, thus 'dragonofruin'