Origin and history of wildly

Old English wilde, "in the natural state, uncultivated" (of plants, herbs), "untamed, undomesticated" (of animals), from Proto-Germanic *wildia-, a word of uncertain origin, perhaps (Watkins) from PIE root *welt- "woodlands; wild" (see wold). Boutkan gives it no IE etymology and finds the only cognate to be Welsh gwyllt "wild."

Of persons, "self-willed, lacking restraint," late Old English; also of a region, "unpeopled, without civilization." Of wind, weather, c. 1200. The specific meaning "sexually dissolute, loose" is attested from mid-13c. The meaning "distracted with excitement or emotion, crazy" is from 1590s. U.S. slang sense of "exciting, excellent" is recorded from 1955.

Baseball wild pitch is recorded from 1867. Wildest dreams attested from 1717. Wild West in a U.S. context recorded by 1826; figurative of any lawless place by 1889. Wild Turkey brand of whiskey (Austin Nichols Co.) in use from 1942. Also see wildcat, wild card, wild goose chase.

As an adverb from 1540s. To do something like wild "with passionate eagerness" is by 1670s. To run wild is by 16c. of domestic animals and cultivated plants, by late 18c. of decivilized human beings.

Ursula ... hath bin at all the Salsbury rasis, dancing like wild with Mr Clarks. [letter, 1674]

Germanic cognates include Old Saxon wildi, Old Norse villr, Old Frisian wilde, Dutch wild, Old High German wildi, German wild, Gothic wilþeis "wild," German Wild (n.) "game."

common adverbial suffix, forming, from adjectives, adverbs signifying "in a manner denoted by" the adjective; Middle English -li, from Old English -lice, from Proto-Germanic *-liko- (source also of Old Frisian -like, Old Saxon -liko, Dutch -lijk, Old High German -licho, German -lich, Old Norse -liga, Gothic -leiko). See -ly (1). It is 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.