The Parliament of the Isle of Man is called Tynwald, and has been running continuously for over 1000 years!
(Kind of strange that the English Parliament is often called "the mother of Parliaments"?!)
It is of Norse origin, and has the same roots as Thingvellir (Iceland) - or more correctly Žingvellir - and the Norwegian Tingvoll.
The name is derived from the Old Norse word Žingvǫllr meaning the meeting place of the assembly, the field (vǫllr→wald, cf. the Old English cognate weald) of the thing.
There is an annual open-air assembly on Old Midsummer's Day; now held on 5th July, Tynwald Day.