"plainly seen or perceived, manifest, obvious," late 14c., from Old French evident and directly from Latin evidentem (nominative evidens) "perceptible, clear, obvious, apparent" from ex "out, out of, fully" (see ex-) + videntem (nominative videns), present participle of videre "to see" (from PIE root *weid- "to see").
common adverbial suffix, forming from adjectives adverbs signifying "in a manner denoted by" the adjective, Middle English, from Old English -lice, from Proto-Germanic *-liko- (cognates: Old Frisian -like, Old Saxon -liko, Dutch -lijk, Old High German -licho, German -lich, Old Norse -liga, Gothic -leiko); see -ly (1). Cognate with lich, and identical with like (adj.).
Weekley notes as "curious" that Germanic uses a word essentially meaning "body" for the adverbial formation, while Romanic uses one meaning "mind" (as in French constamment from Latin constanti mente). The modern English form emerged in late Middle English, probably from influence of Old Norse -liga.
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Definitions of evidently
unmistakably (`plain' is often used informally for `plainly');