Meaning

noun a purposeful or industrious undertaking (especially one that requires effort or boldness)

noun earnest and conscientious activity intended to do or accomplish something

verb attempt by employing effort

originThe verb is from Middle English endeveren (“to make an effort”); the noun is from Middle English endevour, from the verb. Endeveren is from (putten) in dever (“(to put oneself) in duty”), from in + dever (“duty”), partially translating Middle French (se mettre) en devoir (de faire) (“(to make it) one's duty (to do), to endeavour (to do)”) (from Old French devoir, deveir (“duty”)).

Etymology from Wiktionary, CC BY-SA 3.0