The name carbon oxide is too vague. Carbon and oxygen can bond to form more than one possible compound.
CO = carbon monoxide
The name needs to tell us the number of oxygen atoms in the molecules of this compound.
By the way, if molecules of the compound contain only one atom of the first element listed - no prefix is needed for that element. If the first element listed has more than one atom in the molecule, a prefix will be used.
NO = nitrogen monoxide