Gilmore Girls. How did Lorelai become Rory?
It’s explained early on in the show. When Lorelai had Rory she didn’t know what to call her so named her after herself, Lorelai Leigh Gilmore (Leigh is their grandmother on their fathers side, the annoying one). She then started to call her Rory as a nickname as she liked it as it was different, but had already registered her as Lorelai Leigh Gilmore so couldn’t change her name to Rory Leigh Gilmore, so Rory just stuck. Rory doesn’t actually come from Lorelai.