thought it came from “Aubie” and “Barnie”. Instead of calling them “Aubie’s” and “Barnies” we started calling them “Boogies”. So Boogs, Boogereaters, etc. are derivatives of Aubie, which I think was meant to be condescending, but obviously wasn’t insulting enough. So instead of called them “Barners” we call them “Boogers”.

A phrase like “[insert target here] eats boogers” is one of those things that just comes up (its childish, giggle-inducing charm merely catches our attention—as though the very immaturity of it is a core part of its appeal). Plus, it’s much easier to say “_ eat boogers” in mixed company than a lot of other common insults. I’ve heard “Gators eat boogers” for as long as I can remember. But sometimes, these things stick for no apparent reason. Both the Auburn-booger connection and “Gators wear jean shorts” may have stuck because (in addition to being true) they’re just funny; and now, a significant part of their appeal is that they stuck. It’s a linguistic cycle. (cf. “corndog”)

I always thought there was a famous clip of an AU coach digging one out and licking his finger clean…

Then during an LSU-Bama basketball game I was watching I saw this happen.
http://youtube.com/watch?v=VkGff7ciHyU

So naturally I assumed it was a state of Alabama thing…