Senex means elder in Latin and so the Roman Senate was an assembly of elders. Perhaps they were thought to be wiser. They were not elected but appointed by the Consul and they did not actually legislate but deliberated on law proposals from the Consul. Their numbers varied from 100 to several hundred. Despite their seeming lack of power, they had great moral authority.
Many subsequent democracies inherited the name if not the functions of the Senate. In the United States the Congress consists of the House of Representatives and the Senate, which is the higher and more prestigious body.
The French too have an Assemblee Nationale (the lower chamber) and a Senat (the higher chamber)of Parliament.
In Great Britain the Houses of Parliament comprise the House of Commons and the House of Lords.
In Britain the Queen (not being a commoner) is not allowed to enter the House of Commons. That is because in 1642 King Charles I and his armed men came to the House of Commons to arrest five of its members for treason. They had already fled. But since that day no monarch has entered the House of Commons chamber. The State Opening of Parliament takes place in the chamber of the House of Lords. The Throne is not a part of the House of Lords but is the third part of Parliament.
Canada, not surprisingly has an amalgam of the British, French and American systems. They too have a House of Commons and a Senate modeled after the House of Lords.
In Germany the Bundestag was established in 1949 to succeed the Reichstag. With the Bundesrat it constitutes the German legislative body and elects the Chancellor.
The two legislative bodies of Japan (Kokai) are called the Diet in English. This has nothing to do with their eating habits but comes from The Latin “dies” which means “day,” (tag in German) and is also present in Reichstag and Bundestag.
Israel has the Knesset, a unicameral legislative body. The name means Assembly. Curiously Beit ha Knesset is the Hebrew word for synagogue and it means Assembly House.
Ukraine also has a unicameral body called Verkhovna Rada (Supreme Council). It is known for some spectacular brawls and tumultuous physical fights.
Russia, an autocratic state, has nevertheless surrounded itself with all the trappings of a democracy. It has a president, a legislative body and a judicial system. After the fall of the Soviet Union in 1991, the Russian Federation revived the name “State Duma” for the lower house of the Russian Parliament. The name comes from the verb “dumat” which means to think. The irony is that it really does not have to indulge in any thinking at all. All it needs to do is rubber stamp the proposals of Czar Vladimir I who is called their President.
This is of necessity an abbreviated and very incomplete picture of legislative bodies but may perhaps give us some perspective on how some modern nations govern themselves.