Since high school I've been involved in conworlding - collaborative development of fictional worlds and societies, then setting stories or games in them.

Around 2005, I and some friends set a story in a culture with a goddess named Per married to a god named Elith. The religion gets called "Perelithve".

Skip to 2008. Neil Stephenson publishes Anathem, One throwaway reference mentions two of the avout, a woman named Per who marries a man named Elith. The marriage rite they invent gets called "Perelithian"

If names can have between 3 and 8 letters, and always alternate vowels and consonants, and ''th' counts as one sound, I calculate that the chances of someone who needs two names coming up with "Per" and "Elith" is on the order of one in a billion. The similarity in stories maybe adds another two or three bits of unlikelihood. If I've read 1000 novels, each of which has 100 minor characters, and my conworlds contain 1000 characters, then the odds aren't really that bad, maybe as high as 1%

Still freaks me out, though.