Origin and history of absolutely

late 14c., "unrestricted, free from limitation; complete, perfect, free from imperfection;" also "not relative to something else" (mid-15c.), from Latin absolutus, past participle of absolvere "to set free, acquit; complete, bring to an end; make separate," from ab "off, away from" (see ab-) + solvere "to loosen, untie, release, detach," from PIE *se-lu-, from reflexive pronoun *s(w)e- (see idiom) + root *leu- "to loosen, divide, cut apart."

Sense evolution probably was from "detached, disengaged" to "perfect, pure." Meaning "despotic" (1610s) is from notion of "absolute in position;" absolute monarchy is recorded from 1735 (absolute king is recorded from 1610s). Grammatical sense is from late 14c.

Absolute magnitude (1902) is the brightness a star would have at a distance of 10 parsecs (or 32.6 light years); scientific absolute value is from 1907. As a noun in metaphysics, the absolute "that which is unconditional or free from restriction; the non-relative" is from 1809.

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.