Intended to indicate that one might be suffering from Inflated Ego Syndrome (a little-known virus which predominantly affects white male freshman). Symptoms of IES include: wearing of Abercrombie, popped collars (hence the phrase "keep them collars down"), and also may include symptoms of Urban Imitation Disease (UID).
"Hey frosh, nice Abercrombie shirt! Keep them collars down!"
by kingofspain March 26, 2005