Old English luflic "affectionate, loving; loveable;" see love (n.) + -ly (1). Sense of "lovable on account of beauty, attractive" is from c. 1300; in modern use "applied indiscriminately to all pleasing material objects, from a piece of plum-cake to a Gothic cathedral" [George P. Marsh, "The Origin and History of the English Language," 1862]. As an expression of delight, 1610s.
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).
<a href="https://www.etymonline.com/word/loveliness">Etymology of loveliness by etymonline</a>
Harper, D. (n.d.). Etymology of loveliness. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/loveliness