Why is West Virginia called West Virginia?

The western counties of Virginia had long had differences with the eastern counties. When the Civil War began and Virginia seceded from the Union, the western counties seceded from Virginia to remain part of the Union, initially as a loyal government of the Commonwealth of Virginia. In 1863 those counties were admitted to the Union as the State of West Virginia. As a result, after the war they did not have to again become part of the then defeated Commonwealth of Virginia.