quaff v.

"to drink or swallow in large draughts," 1510s (implied in quaffer), a word of obscure origin, perhaps imitative, or perhaps from Low German quassen "to overindulge (in food and drink)," with -ss- misread as -ff-. Related: Quaffed; quaffer; quaffing. The noun, "act of quaffing; the amount of liquor drunk at once," is attested by 1570s, from the verb.