wallop (v.) late 14c., "to gallop," possibly from Old North French *waloper (13c., Old French galoper), from Frankish compound *walalaupan "to run well" (compare Old High German wela "well," see well (adv.); and Old Low Franconian loupon "to run, leap," from Proto-Germanic *hlaupan; see leap (v.)).

The earliest known use of the noun wallop is in the Middle English period (1150—1500). OED's earliest evidence for wallop is from before 1375, in William of Palerne. wallop is a borrowing from French.

From Middle English wallopen (“gallop”), from Anglo-Norman [Term?], from Old Northern French walop (“gallop”, noun) and waloper (“to gallop”, verb) (compare Old French galoper, whence modern French galoper), from Frankish *wala hlaupan (“to run well”) from *wala (“well”) + *hlaupan (“to run”), from Proto-Germanic *hlaupaną (“to run, leap, spring”), from Proto-Indo-European *klaub- (“to spring, stumble”).

The surname Wallop was first found in Hampshire where "the true and original name of this family is Barton - Peter Barton, lord of West Barton, having married Alice, only daughter and heiress of Sir Robert de Wallop, who died in the eleventh year of Edward I."

Wallop is a colloquial term for ‘beer’ (or loosely, for any ale drink). It is usually regarded as a Briticism, although the first known instance of its use (in 1933) is Australian.