 Gilfillan recorded their meaning, "according to some, Neighbor lake, according to others a lake somewhere," possibly referring to the neighbouring Rainy Lake and to Lake Couchiching located in southern Ontario.Early European (French) inhabitants gave the names "Lac à la Pluie" (Rainy Lake) and "Rivière à la Pluie" (Rainy River) to the nearby bodies of water because of the mist-like rain present at the falls of Rainy River and then to the settlement that became known as International Falls.About 10,000 years ago almost 90% of Koochiching County was covered by Lake Agassiz.