(A ). A chap. The French bouffer (older form, bauffer) meant to eat, as il bauffera tout seul. If this is the basis of the word, a buffer is one who eats with us, called a Commoner in our universities.
“I always said the old buffer would.” —Miss Braddon: Lady Audley's Secret.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894