Molecular formula of carbon monoxide is CO.
It contains one atom each of carbon and oxygen by covalent bonding.
To name a covalent compound, the first element is named the same as its element name.
For the second element, a suffix "-ide" is added to first part of its element name. So for oxygen, it is oxide.
To denote the number of atoms of each element, the prefix "mono" for one atom, "di" for 2 atoms, "tetra" for 4 atoms is added.
So, name for CO should be monocarbon mono oxide.
By convention, mono is not written for first element and two 'o' in monooxide are replaced by one 'o'.
Therefore name is CARBON MONOXIDE