Here's why:

* Iron (Fe) can exist in multiple oxidation states. In this case, oxygen has an oxidation state of -2, and since there's only one oxygen atom, iron must have an oxidation state of +2 to balance the charge.

* (II) indicates that the iron ion has a +2 charge.

* Oxide refers to the oxygen anion (O²⁻).

Therefore, the systematic name combines the metal name with its oxidation state followed by the nonmetal anion name.