Offline, my deadname had a lot of nicknames. Which, I obviously will not share for obvious reasons.
If I eventually come out to more people, and give them my preferred name, I don't think I'd want people to give me a nickname with Kory since it's already a rather short name to begin with. It's fine as it is.
For my username, people often shorten it to Pala, and I ended up using Pala in every single video game I play ever now, so in ways, you can say that online nickname stuck since I use it in everything in video games. Guess you can now call it my "IGN" (in game name video game name world)? I wish I knew who started that nickname for me when I started going by Palamon as a username, but it's been so long now I've since long forgotten.