Etymology
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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 meaning "to thrash" (1820) and the noun meaning "heavy blow" (1823) may be separate developments, of imitative origin. Related: Walloped; walloping.
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gallop (v.)
"move or run by leaps," early 15c., from Old French galoper "to gallop" (12c.), central Old French form of Old North French waloper, probably from Frankish *wala hlaupan "to run well" (see wallop). Related: Galloped; galloping. Though the French word is Germanic, Dutch galopperen, German galoppiren, Swedish galoppera are from French.
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codswallop (n.)

said to be from 19c. (but first attested 1959), perhaps from wallop, British slang for "beer," and cod in one of its various senses, perhaps "testicles" (a 1966 citation in OED spells it cod's wallop).

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