cheerful (adj.)

c. 1200, "the face, countenance," especially as expressing emotion, from Anglo-French chere "the face," Old French chiere "face, countenance, look, expression," from Late Latin cara "face" (source also of Spanish cara), possibly from Greek kara "head" (from PIE root *ker- (1) "horn; head"). From mid-13c. as "frame of mind, state of feeling, spirit; mood, humor."

By late 14c. the meaning had extended metaphorically to "state or temper of mind as indicated by expression." This could be in a good or bad sense ("The feend ... beguiled her with treacherye, and brought her into a dreerye cheere," "Merline," c. 1500), but a positive sense, "state of gladness or joy" (probably short for good cheer), has predominated since c. 1400.

The meaning "that which makes cheerful or promotes good spirits" is from late 14c. The meaning "shout of encouragement" is recorded by 1720, perhaps nautical slang (compare the earlier verbal sense "encourage by words or deeds," early 15c.). The antique English greeting what cheer? (mid-15c.) was picked up by Algonquian Indians of southern New England from the Puritans and spread in Native American languages as far as Canada.

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

word-forming element attached to nouns (and in modern English to verb stems) and meaning "full of, having, characterized by," also "amount or volume contained" (handful, bellyful); from Old English -full, -ful, which is full (adj.) become a suffix by being coalesced with a preceding noun, but originally a separate word. Cognate with German -voll, Old Norse -fullr, Danish -fuld. Most English -ful adjectives at one time or another had both passive ("full of x") and active ("causing x; full of occasion for x") senses.

It is rare in Old English and Middle English, where full was much more commonly attached at the head of a word (for example Old English fulbrecan "to violate," fulslean "to kill outright," fulripod "mature;" Middle English had ful-comen "attain (a state), realize (a truth)," ful-lasting "durability," ful-thriven "complete, perfect," etc.).