Commutative, from commutation, which means exchange, trade, or replacement according to the first 2 definitions. The commutative property says that the order in which the operation is carried out does not matter. You can exchange/trace factors or addends and still arrive at the same product or sum.
Definition one of the adjective form gives "involving substitution, interchange"
So you just switch or commute the two addends or factors and get the same sum or product!