Etymology: < Anglo-Norman and Middle French advers (c1150 as adjective and noun), variant (with remodelling after the ulterior Latin etymon) of Anglo-Norman and Middle French avers hostile, opposed, antagonistic (c1100 in Old French; see also averse adj.) and its etymon classical Latin adversus turned towards, facing, opposite, in opposition, hostile, opposed, unfavourable, harmful, use as adjective of past participle of advertere advert v. Compare Old Occitan advers (1319; compare also avers (1330)), Catalan advers (13th cent.), Spanish adverso (14th cent.; compare †averso (c1275)), Portuguese adverso (15th cent.), Italian avverso (end of the 13th cent.; mid 13th cent. as averso ; also †adverso (second half of the 13th cent.)). With use as noun compare classical Latin adversus (masculine) opponent, adversum (neuter) obstacle, hindrance, difficulty, trouble, misfortune, adversity, opposite or contrary state of affairs. Compare averse adj., averse n., and the Romance forms cited at these entries.The position of stress has varied in the history of the word, and in current usage both first- and second-syllable stress is common, although for most of the 20th cent. (up to its revised ed. 14, 1989) D. Jones Eng. Pronouncing Dict. records only first-syllable stress.

Etymology: Originally < Anglo-Norman adverser to oppose, to resist (a thing or person) (c1150; more usually averser ; compare Middle French adverser , averser , in same sense (second half of the 15th cent.)) and its etymon classical Latin adversārī to oppose, resist, to be opposed to < adversus adverse adj. In later use probably independently re-formed < adverse adj.