Marsicus
Could not find Marsico in Logeion dictionaries.
Marsico Proper-name adjective: neuter dative singular, Proper-name adjective: masculine ablative singular, Proper-name adjective: masculine dative singular, Proper-name adjective: neuter ablative singular of Marsicus
Mārsĭcus, (14) a, um, des Marses : Cic. Div. 1, 99 ; Agr. 2, 90 ; Mart. 13, 121, 1.