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.
