Mac Shiúrtáin
Mac SHIÚRTÁIN—V—M'Shurtayne, M'Shurdan, M'Shordane, M'Jordaine, Jourdan, Jordan, Jurdan, &c.; 'son of Jordan' (see Siúrdán); a patronymic surname assumed by the descendants of Jordan D'Exeter, an Anglo-Norman family who settled in Co. Mayo, but in 1571 were, according to Campion, 'very wild Irish.' The initial S of the second part of the surname is now always aspirated, and the pronunciation is often Ó Ciúrtáin.
Alphabetical Index to Irish Surnames