"slaughterhouse for cows," 1820, from French abattre in its literal sense "to beat down, knock down, slaughter" (see abate) + suffix -oir, corresponding to Latin -orium, indicating "place where" (see -ory).
c. 1300, "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.
adjective and noun suffix, "having to do with, characterized by, tending to, place for," from Middle English -orie, from Old North French -ory, -orie (Old French -oir, -oire), from Latin -orius, -oria, -orium.
Latin adjectives in -orius, according to "An Etymological Dictionary of the French Language," tended to "indicate a quality proper to the action accomplished by the agent; as oratorius from orator; laudatorius from laudator. The neuter of these adjectives was early employed as a substantive, and usually denoted the place of residence of the agent or the instrument that he uses; as praetorium from praetor; dormitorium from dormitor; auditorium, dolatorium.
"These newer words, already frequent under the Empire, became exceedingly numerous at a later time, especially in ecclesiastical and scholastic Latin; as purgatorium, refectorium, laboratorium, observatorium, &c." [transl. G.W. Kitchin, Oxford, 1878]
<a href="https://www.etymonline.com/word/abattoir">Etymology of abattoir by etymonline</a>
Harper, D. (n.d.). Etymology of abattoir. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/abattoir