My user name, Innegativeion, (pronounced "in-negative ion", by the way) was actually inspired by a high school chemistry teacher.
See, he never bothered memorizing anyone's name, like at all. So instead, he had a nickname for every single student. My real name is Ian, so he would call me ion. For some reason I never made the incredibly obvious similarities between my name and an atom that has lost or gained an electron, and found it rather clever.
So that's where the ion comes from. The rest, well basically it's nonsense humor while also trying to be easy to say. "In"negative of course implies not negative. An ion without a negative charge would have a positive charge, so why not just say it's positive? Yeah, kind of silly... but it sounds cool.