Classical scholars will spot the wintry associations of this word; it derives from Latin nix for snow, which becomes niv- in compounds such as nivālis, snowy or snow-covered. Etymologists point out that the English snow and the Latin nix both ultimately derive from the same ancient Indo-European root. But then humans in Europe have long had plenty of experience of the white stuff.
About four centuries ago, English scholars borrowed nivālis to make the adjective nival to add to our snowy (though French got there first, at least a century earlier). We also have the more recent technical term nivation, not — as you might guess — meaning snowfall but the erosion of ground around and beneath a snow bank that is seasonally melting.
Subnivean is another member of the group, nearly two centuries old. This refers to something that happens underneath snow such as the activities of animals that survive winter beneath it.
Very recently that word has been joined by the linked noun subnivium for the area between soil surface and snowpack. It was coined by a group led by Jonathan Pauli of the University of Wisconsin-Madison. They wrote in a paper in Frontiers in Ecology and the Environment in June 2013: “For many terrestrial organisms in the Northern Hemisphere, winter is a period of resource scarcity and energy deficits, survivable only because a seasonal refugium — the ‘subnivium’ — exists beneath the snow.”