Cúisín
CÚISÍN—XII—Coushine, Cushine, Cousin, Cushen, Cussen Cousins, etc.; Norman 'le cosyn,' i.e., the cousin, kinsman; the name of an Anglo-Norman family who settled in Ireland soon after the invasion; found in nearly all the counties of Munster, and also in Connacht and Westmeath.
Alphabetical Index to Irish Surnames