c. 1400, "full of cheer, having good spirits," from cheer (n.) + -ful. Meaning "elevating the spirits" is from mid-15c. Related: Cheerfully; cheerfulness.

"showing good spirits," mid-15c., from cheer (n.) + -y (2). The colloquial alternative to cheerful. Related: Cheerily; cheeriness.

"to make cheerful, lively, or merry; render glad or joyous," 1530s, from Latin exhilaratus "cheerful, merry," past participle of exhilarare "gladden, cheer," from ex "out, out of; thoroughly" (see ex-) + hilarare "make cheerful," from hilarus "cheerful" (see hilarity). Related: Exhilarated; exhilarating.

1823, "cheerful," from Latin hilaris "cheerful, lively, merry, joyful, of good cheer" (see hilarity) + -ous. Meaning "boisterously joyful" is from 1835. Related: Hilariously.

"act of enlivening or cheering; state of being enlivened or cheerful," 1620s, from Late Latin exhilarationem (nominative exhilaratio) "a gladdening," noun of action from past-participle stem of exhilarare "gladden, cheer," from ex "out, out of; thoroughly" (see ex-) + hilarare "make cheerful," from hilarus "cheerful" (see hilarity).

Old English sunnebeam; see sun (n.) + beam (n.). As "cheerful person" from 1886.

late 14c., gladsum "glad, joyful, cheerful;" see glad (adj.) + -some (1).

"full of gaiety, cheerful," 1724, from blithe + -some (1). An adjective from an adjective. Related: Blithesomely; blithesomeness.

also lighthearted, "cheerful," c. 1400, from light (adj.1) + -hearted. Related: Light-heartedly; light-heartedness.

1721 as a musical term, from Italian allegro "brisk, sprightly, cheerful," from Latin alacrem (nominative alacer) "lively, cheerful, brisk" (see alacrity). The same Latin word came into English 17c. as aleger "lively, brisk," from Old French alegre, from Latin alacris; and Milton used "L'Allegro" in its literal sense as a poem title (1632).