Where did this fanfic/fanart trope come from?

Recently I've been seeing quite a bit of fanarts, and to a lesser extent fanfics, where Rhaenys (daughter of Rhaegar) gets a silver streak of hair alongside her canon Dornish-looking features of brown skin and dark hair. Does anyone know if it started in a fic somewhere, or is it just something that someone started doing and the fandom just started copying it?