Operation
late Middle English: via Old French from Latin operatio(n- ), from the verb operari ‘expend labour on’ (see operate).
wiktionary
From Middle French operation, from Old French operacion, from Latin operātiō, from the verb operor(“I work”), from opus, operis(“work”). Equivalent to operate + -ion.
etymonline
operation (n.)
late 14c., "action, performance, work," also "the performance of some science or art," from Old French operacion "operation, working, proceedings," from Latin operationem (nominative operatio) "a working, operation," noun of action from past-participle stem of operari "to work, labor" (in Late Latin "to have effect, be active, cause"), from opera "work, effort," related to opus (genitive operis) "a work" (from PIE root *op- "to work, produce in abundance").
The surgical sense of "act or series of acts performed upon a patient's body," usually with instruments, is first attested 1590s. The military sense of "act of carrying out a preconcerted series of movements" is by 1749.
