When Peri introduces himself, he says “I changed my name to Peri, LIKE Periwinkle”, which may imply that he just got the idea for the name Peri from the word Periwinkle. He doesn’t say “I changed my name to Peri SHORT FOR Periwinkle”, and I don’t think there are any other scenes where he’s called Periwinkle from what I can remember. I don’t know if this has been discussed before, but I’ve been thinking about this for days and it’s driving me nuts.