 In the meaning "water-route" or "water-body", *Kainu- was originally a toponymic prefix in SW Finland, and during the Iron Age it was gradually established as the name of the land surrounding the northern coasts Bothnian Gulf.Linguistically this etymology is seen as more acceptable.The area originally known as Kainuu seems to have been the central part of Ostrobothnia where Karelians could access the Gulf of Bothnia in the Middle Ages, giving also conceptual support for the theory.