diet [LME] In the context of food diet reaches back to Greek diaita ‘way of life’. In the context of government and administration, for example, as the name of the legislative assembly in some European countries, diet comes from medieval Latin dieta, which, which probably came from Latin dies ‘day’ and meant both ‘a day’s work or pay’ and ‘meeting’. Martin Luther committed himself to the cause of Protestant reform at the Diet of Worms, a meeting of the imperial diet of the Holy Roman Emperor Charles V in 1521 in the German town of Worms on the Rhine.