Green’s Dictionary of Slang

(US campus) someone who is socially unacceptable, who does not fit in.

1990		Eble Campus Sl. Oct. 3: large cheddar – unattractive person.
1996		Eble Sl. and Sociability 120: During 1990–92, all of the following nouns categorized someone as not attuned to the prevailing style or priorities of UNC-CH student life: [...] cheddar, cheese, cheeseball, cheeser.