Mouseburger

Mouseburger \mous.BUR-ger\ , noun;
1. A young woman of unexceptional appearance and talents, regarded as timid, dowdy, or mousy

Originally mouseburger referred to a mousy young woman who, despite her unexceptional appearance and talents, achieves professional and personal success through determination. It is first attested in 1971 and is a play on mouse ("a timid or retiring person"). This is the first attestation of the slang suffix -burger, which took root in the early 1980's. It is used to "form nouns denoting persons characterized by the initial element" and is a play on the practice of changing to first element of hamburger to denote what kind of type of burger it is (e.g. cheeseburger, veggie burger, etc.).