late 13c., verray "true, real, genuine," later "actual, sheer" (late 14c.), from Anglo-French verrai, Old French verai "true, truthful, sincere; right, just, legal," from Vulgar Latin *veracus, from Latin verax (genitive veracis) "truthful," from verus "true" (source also of Italian vero), from PIE root *were-o- "true, trustworthy." Meaning "greatly, extremely" is first recorded mid-15c. Used as a pure intensive since Middle English.
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 verily from WordNet
in truth; certainly; "trust in the Lord...and verily thou shalt be fed"- Ps 37:3;