To calve is what English says when a cow — or another animal whose baby is called a calf, such as a whale or a deer — gives birth. A farmer might say the cow is going to calve tonight. City speakers more often say have a calf or give birth; calve belongs to farms, vets, and nature writing. Though actually, the same verb is stretched to ice: when a wall of glacier ice breaks off and falls into the sea, people say the glacier calves. That picture grew from the animal sense, not from a different spelling.