gleeful adj.

Old English gliu, gliw, gleow "entertainment, mirth (usually implying music); jest, play, sport," also "music" and "mockery," presumably from a Proto-Germanic *gleujam but absent in other Germanic languages except for the rare Old Norse gly "joy;" probably related to the group of Germanic words in gl- with senses of "shining; smooth; radiant; joyful" (compare glad), from PIE root *ghel- (2) "to shine." A poetry word in Old English and Middle English, obsolete c. 1500-c. 1700, it somehow found its way back to currency late 18c. In Old English, an entertainer was a gleoman (female gleo-mægden).

Glee club (1814) is from the secondary sense of "musical composition for three or more solo voices, unaccompanied, in contrasting movement" (1650s), a form of musical entertainment that flourished 1760-1830.

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.).