A freshman or greenhorn. This term is employed in the French and Scotch universities, and is evidently a corruption of bec jaune (yellow beak), a French expression to designate a nestling or unfledged bird. In the university of Vienna the freshman is termed beanus, and in France footing-money is bejaunia.
“His grandmother yielded, and Robert was straightway a bejan or yellow-beak.” —Macdonald: R. Falconer.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894