The name of the legislative body was originally "Parlamentum" during the Middle Ages, the "Diet" expression gained mostly in the early modern period.
[8] The first exact written mention of the word "parlamentum" (parliament) for the nationwide assembly originated during the reign of King Andrew II in the Golden Bull of 1222, which reaffirmed the rights of the smaller nobles of the old and new classes of royal servants (servientes regis) against both the crown and the magnates, and to defend the rights of the whole nation against the crown by restricting the powers of the latter in certain fields and legalizing refusal to obey its unlawful/unconstitutional commands (the "ius resistendi").
However, under the rule of autocratic kings like Louis the Great and the early absolutist Matthias Corvinus, parliaments were often summoned merely to formalize royal decisions, which members were obliged to approve to meet constitutional requirements, thus it had no significant power of its own.
In 1492, the Diet limited all serfs' freedom of movement and greatly expanded their obligations while at the same time only a few peasant families were prospering because of increased cattle exports to the West.
Shocked by the peasant revolt, the Diet of 1514 passed laws that condemned the serfs to eternal bondage and increased their work obligations further.
Before the development of the society of estate, the Diet consisted of the lords and the leaders of the church, but then the voting base was extended to the common nobility and the elected representatives of Royal free cities.
One of the key words of the Revolution of '48 was the taking away the privileges of the nobles and oligarchs, so currently there is an unicameral system, to guarantee the rule of the people.
In the course of the Hungarian Revolution of 1848 a diet was called at Pest that was dismissed by decree of Emperor Ferdinand I of Austria in October; the next year a Hungarian assembly met at the Protestant Great Church of Debrecen, which declared the new Emperor Franz Joseph deposed and elected Lajos Kossuth regent-president.
The revolution was finally suppressed by Austrian troops under General Julius Jacob von Haynau and the assembly dissolved.
In 1860 Emperor Franz Joseph issued the October Diploma, which provided a national Reichsrat assembly formed by delegates deputed by the Landtage diets of the Austrian crown lands, followed by the February Patent of 1861, promising the implementation of a bicameral legislature.
Finally in the course of the Austro-Hungarian Compromise of 1867, the emperor appointed Gyula Andrássy Hungarian minister-president and the re-established national assembly convened on 27 February.
The House of Representatives (Képviselőház) consisted of members elected, under the Electoral Law of 1874, by a complicated franchise based upon property, taxation, profession or official position, and ancestral privileges.
According to Randalph Braham, the increasingly illiberal nature of the Diet, leading into World War II, over the period from 1867 and 1944, continues to be a sticking point in regional cultural and political conflicts to this day.