I don't know what it is about this fic - how do people stumble on it?

It's one of those mysteries when one of your fics becomes popular (for a NNF definition of 'popular') and suddenly is gaining kudos, and you're not quite sure how people got there in the first place...

I do rather wish that AO3 had a 'trackback' option, so you could see where people came from. I'd love to know where people stumbled onto my fics from!