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fortunate (adj.)[fortunate 词源字典]: late 14c., "having good fortune; bringing good fortune," from Latin fortunatus "prospered, prosperous; lucky, happy," past participle of fortunare "to make prosperous," from fortuna (see fortune). Fortunate Islands "mythical abode of the blessed dead, in the Western Ocean" (early 15c.; late 14c. as Ilondes of fortune) translates Latin Fortunatae Insulae.[fortunate etymology, fortunate origin, 英语词源]
fortunately (adv.): "by (good) fortune," 1540s, from fortunate + -ly (2).
unfortunate (adj.): mid-15c., "unlucky," from un- (1) "not" + fortunate (adj.). Infortunate in same sense is from late 14c. (along with a verb infortune "to render unhappy"). In late 18c.-early 19c., unfortunate woman was a polite way to say "prostitute." The noun meaning "one who is not fortunate" is recorded from 1630s.
unfortunately (adv.): 1540s, "in an unfortunate manner, by ill-fortune," from unfortunate + -ly (2). The original meaning is now rare; the main modern sense of "sad to say, unhappily, unluckily," in parenthetical use, is recorded from 1770s.