Bumper.

A full glass, generally connected with a “toast.” Dr. Arn says a bumper is when the surface of the wine bumps up in the middle. (French, bomber, to render convex, to bulge or swell out.)

“A fancied connection with hump, a swelling, has not only influenced the form of the word, but [has] added the notion of fulness.”—Skeat: Etymological Dictionary.