”In the 11th century, in North-Russia started settling the coasts of the White Sea, named so for being ice-covered for over half of a year. The mixed ethnic group of the Karelians and the Russians in the North-Russia that lived on the shores of the Arctic Ocean became known as Pomors (”seaside settlers”). Gradually they developed a special type of small one- or two-mast wooden sailing ships, used for voyages in the ice conditions of the Arctic seas and later on Siberian rivers. These earliest icebreakers were called kochi. ” wikipedia/icebreaker

Ship during winter, before modern icebreakers..