Diet (assembly)

In politics, a diet /ˈdaɪət/ is a formal deliberative assembly. The term is mainly used historically for the Imperial Diet, the general assembly of the Imperial Estates of the Holy Roman Empire, and for the legislative bodies of certain countries. Modern usage mainly relates to the Kokkai of Japan, called "Diet" in English, or the German Bundestag, the Federal Diet.

The term (also in the nutritional sense) is derived from Medieval Latin dieta, meaning both "parliamentary assembly" and "daily food allowance", from earlier Latin diaeta transcribing Classical Greek δίαιτα diaita, meaning "way of living", and hence also "diet", "regular (daily) work".

Through a false etymology, reflected in the spelling change replacing ae by e, the word came to be associated with Latin dies, "day". The word came to be used in the sense of "an assembly" because of its use for the work of an assembly meeting on a daily basis, and hence for the assembly itself. The association with dies is reflected in the German language use of Tagung (meeting) and -tag (not only meaning "day", as in Montag—Monday—but also "parliament", "council", or other law-deliberating chamber, as in Bundestag or Reichstag).

In this sense, it commonly refers to the Imperial Diet assemblies of the Holy Roman Empire:

...
Wikipedia