mid-14c., "mocking, derisive;" c. 1400, "disdainful;" see scorn (n.) + -ful. From 1560s as "provoking or exciting contempt." Scorny was 19c. U.S. colloquial. Related: Scornfully; scornfulness. An older adverb was scornliche (c. 1300).
late 12c., scorn, skarn, "feeling or attitude of contempt; contemptuous treatment, mocking abuse," a shortening of Old French escarn "mockery, derision, contempt," a common Romanic word (Spanish escarnio, Italian scherno) of Germanic origin (source also of Old High German skern "mockery, jest, sport;" see scorn (v.)).
The vowel is perhaps influenced by Old French escorne "affront, disgrace," which is a back-formation from escorner, literally "to break off (someone's) horns" (see the verb). To laugh (someone) to scorn is from c. 1300 ("Sir Bevis").
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.).
<a href="https://www.etymonline.com/word/scornful">Etymology of scornful by etymonline</a>
Harper, D. (n.d.). Etymology of scornful. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/scornful