"laugh at in contempt, mock, ridicule, scorn by laughter," 1520s, from French derider, from Latin deridere "to ridicule, laugh to scorn," from de "down" (see de-) + ridere "to laugh" (see risible). Related: Derided; deriding.
active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.
As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.
1550s, "given to laughter," from French risible (14c.) and directly from Late Latin risibilis "laughable, able to laugh," from Latin risus, past participle of ridere "to laugh," a word which, according to de Vaan, "has no good PIE etymology." Meaning "laughable, capable of exciting laughter, comical" is by 1727. Related: Risibility.
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Definitions of deride from WordNet
treat or speak of with contempt;
He derided his student's attempt to solve the biggest problem in mathematics