Green’s Dictionary of Slang

(US campus) someone who is out of date, unfashionable.

1985		Eble Campus Sl. Oct.
1996		Eble Sl. and Sociability 37: Two kinds of shortening reduce words to letters. The dominant type in college slang is initialism, which names the individual letters: [...] PQ (polyester queen) ‘someone who is out of date’.