it was a term only appplicable to those from the Union, rather than from the Confedracy.

It is a term applicable to nobody. To someone from Europe it is refers to somoeone from the United States, to someone from the southern United States it refers to someone from the northern United States; to someone from the northern United States it refers to someone from New England, to someone from New England it refers to someone from Vermont and to someone from Vermont it refers to someone from New Hampshire.