Meaning

noun anything indispensable

adjective absolutely essential

adjective unavoidably determined by prior circumstances

originFrom Middle English necessarye, from Old French necessaire, from Latin necessārius (“unavoidable, inevitable, required”), variant of necesse (“unavoidable, inevitable”), probably from ne or non cessum, from the perfect passive participle of cēdō (“yield; avoid, withdraw”); see cede. Older use as a noun in reference to an outhouse or lavatory under the influence of English and Latin necessārium, a…

Etymology from Wiktionary, CC BY-SA 3.0