"Trondheim was named Kaupangen (English: market place or trading place) by Viking King Olav Tryggvason in 997. Fairly soon, it came to be called Nidaros. In the beginning it was frequently used as a military retainer (Old Norse: "hird"-man) of King Olav. It was frequently used as the seat of the king, and was the capital of Norway until 1217."