Marsicus
Could not find Marsicum in Logeion dictionaries.
Marsicum proper-name adjective neuter vocative singular, proper-name adjective masculine genitive plural, proper-name adjective masculine accusative singular, proper-name adjective neuter genitive plural, proper-name adjective neuter nominative singular, proper-name adjective neuter accusative singular of Marsicus
Mārsĭcus, (14) a, um, des Marses : Cic. Div. 1, 99 ; Agr. 2, 90 ; Mart. 13, 121, 1.