Dayz has been a handle used online since 1997. It originated from a AOL screename which "Ina" or "Dayz" could have been chosen. Dayz was chosen and has been known in online hacking communities ever since.
When you run with a group of people on DayZ for a fat minute, then switch up to play with someone new for a few days while appearing offline, only to have your friends join the party on alt accounts to find you and said person together.
Squad: I can't believe you, I thought you were rollin with us?
Victim: I am, I'm just---
Squad: I don't wanna hear it. I can't believe you're DayZ Cheating on us.