Senate of Elwynn
The name of the Senate and the elections to it was based on the Senate of Hurmu. As such, upon Hurmu's merger with the Elwynnese Realm in 1573, the Hurmu constitutional terms Prince and Senate were transferred to Elwynn.
The Senate was therefore originally an elected legislature, where its own members elected new members to it. After some time, however, it became an appointed legislature where the Prince appointed any new members to it.