early 15c., "in a God-like manner;" 1580s, "excellently, in the supreme degree;" from divine (adj.) + -ly (2).
Entries linking to divinely
divine adj.
late 14c., "pertaining to, of the nature of, or proceeding from God or a god; addressed to God," from Old French divin, devin (12c.), from Latin divinus "of a god," from divus "of or belonging to a god, inspired, prophetic," related to deus "god, deity" (from PIE root *dyeu- "to shine," in derivatives "sky, heaven, god").
Weakened sense of "excellent in the highest degree, heavenly" had evolved by late 15c. The phrase divine right, indicating one conferred by or based on ordinance of God, is from c. 1600.
-ly 2
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.