Meaning

noun a prescribed selection of foods

verb follow a regimen or a diet, as for health reasons

noun a legislative assembly in certain countries (e.g., Japan)

originFrom Middle English diet, dyet, from Old French diete, from Medieval Latin diēta, diaeta (“a public assembly; set day of trial; a day's journey”), from Ancient Greek δῐ́αιτα (dĭ́aita, “way of living, living space; decision, judgement”), influenced by Latin diēs (“day”).

Etymology from Wiktionary, CC BY-SA 3.0