Did your campus have any local nicknames for national organizations?
For example, at W&L, Sigma Phi Epsilon wasn't usually called SigEp, but "SPE." (I've heard this is common in the south?). I hardly heard anyone ever call them SigEp.
No one at W&L ever called Pi Kappa Alpha "Pike" either. They always said "Pika."
The one that was weirdest is that Pi Kappa Phi was NEVER called Pi Kapp. It was called "Pi Phi."

This was weird because Pi Beta Phi was also on campus (my chapter!). So everyone would refer to them as "girl Pi Phi" and "guy" Pi Phi." I'm not even kidding about that.
The guys at Pi Kappa Phi said that it was supposedly based on some crazy thing they did long ago, the national organization told them they no longer had the right to be called "Pi Kap" but had to be called "Pi Phi" as punishment. The story went that the amount of time they had to be called "Pi Phi" had already expired but the name had just stuck. The whole thing doesn't really ring true to me (why would their nationals decree such a thing?) and sounds like an urban legend to me.
If I had to guess why it was, I think it's more likely that Pi Kappa Phi had a distinctive name to distinguish it from Phi Kappa Sigma, which was usually called "Phi Kap" and not "the Skulls." (Skulls was used occasionally but Phi Kap was far more common.) Because "Pi Kap" and "Phi Kap" sound alike sort of, and for years there were no women at W&L and thus no reason to worry about getting confused with Pi Beta Phi. (W&L went co-ed in '85, sororities came in '89, and Pi Phi came in '92). But who knows if my guess is correct?
Anyway, do you know of other instances of things like this happening on your campus with unusual or nonstandard nicknames for orgs?