Found via the text "The name is a cognate of the names of several legislatures in other Germanic countries, such as the Reichstag in Germany, the Riksdag in Sweden, or the Riksdag in Finland. (For a discussion of the traditional Germanic councils that gave root to bodies such as these, see the article on Ting-style councils.)" in @clacke's link to https://en.wikipedia.org/wiki/Rigsdagen