The Sámi name of the island, "Romsa", is assumed to be a loan from Norse – but according to the phonetical rules of the Sami language the frontal "t" has disappeared from the name. However, an alternative form – "Tromsa" – is in informal use. There is a theory that holds the Norwegian name of Tromsø derives from the Sámi name, though this theory lacks an explanation for the meaning of "Romsa". A common misunderstanding is that Tromsø's Sámi name is "Romssa" with a double "s". This, however, is the accusative and genitive form of the noun used when, for example, writing "Tromsø Municipality" (Roms"s"a Suohkan).