rebate (v.)

c. 1300, abaten, "put an end to" (transitive); early 14c., "to grow less, diminish in power or influence" (intransitive); from Old French abatre "beat down, cast down, strike down; fell, destroy; abolish; reduce, lower" (Modern French abattre), from Vulgar Latin *abbatere, from Latin ad "to" (see ad-) + battuere "to beat" (see batter (v.)). The French literal sense of "to fell, slaughter" is in abatis and abattoir. Related: Abated; abating.

"rectangular groove or channel cut out of the edge of a board or piece of stone so that it will join by overlapping with the next piece, similarly cut," late 14c., rabet, from Old French rabat "a recess in a wall, a lower section," literally "a beating down or back," a back-formation from rabattre "to beat down, beat back" (see rebate (v.); the noun is a doublet of this word).

The verb, meaning "to groove or fit (boards, etc.) by cutting rabbets" is attested from mid-15c. (implied in rabatted, rabetynge); Middle English also had rabet "joiner's plane, rabbet-plane" (mid-15c., from Old French rabot).