"in a friendly manner, without controversy," 1630s, from amicable + -ly (2).
Entries linking to amicably
amicable adj.
early 15c., "pleasant," from Late Latin amicabilis "friendly," a word in Roman law, from Latin amicus "friend," ultimately from amare "to love" (see Amy). In modern use "characterized by friendliness, free from hard feelings, peaceable, socially harmonious." Compare amiable, which is the same word through French. Related: Amicableness.
-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.