Entries linking to splendidly
1620s, "marked by grandeur," probably a shortening of earlier splendidious (early 15c.), from Latin splendidus "bright, shining, glittering; sumptuous, gorgeous, grand; illustrious, distinguished, noble; showy, fine, specious," from splendere "be bright, shine, gleam, glisten," from PIE *splnd- "to be manifest" (source also of Lithuanian splendžiu "I shine," Middle Irish lainn "bright"). An earlier form was splendent (late 15c.). From 1640s as "brilliant, dazzling;" 1640s as "conspicuous, illustrious; very fine, excellent." Ironic use (as in splendid isolation, 1843) is attested from 17c.
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.