Why was "tantrum" trending last week?
late 14c., "repeat, say again," from Old French rendre "give back, present, yield" (10c.), from Vulgar Latin *rendere (formed by dissimilation or on analogy of its antonym, prendre "to take"), from Latin reddere "give back, return, restore," from red- "back" (see re-) + comb. form of dare "to give" (see date (n.1)).
Meaning "hand over, deliver" is recorded from late 14c.; "to return" (thanks, a verdict, etc.) is attested from late 15c.; meaning "represent, depict" is first attested 1590s. Irregular retention of -er in a French verb in English is perhaps to avoid confusion with native rend (v.) or by influence of a Middle English legalese noun render "a payment of rent," from French noun use of the infinitive. Related: Rendered; rendering.
1580s, agent noun from rend (v.).