Costello (surname) to a Gaelic translation of Jocelyn, Jocelyn d'Angulo's given name. In fact, MacOisdealbhaigh is the Gaelic translation of his brother Hostilo (or Hostilio) d'Angulo's first name. Oisdealbh is a much more obvious translation of Hostilo. It is Hostilo's descendants who would bear the surname Mac Oisdealbhaigh (son of Oisdealbh or Hostilo). The surname would later be anglicized to Costello, Costelloe, and Costellow. Gilbert d'Angulo is also sometimes listed as the son of Jocelyn d'Angulo in error. Gilbert d'Angulo is the father of both Jocelyn and Hostilo. It occasionally has been adopted as a pseudonym or stage name by famous people
Irish people used. While both "Mac" and "Ó'" prefixes are Gaelic in origin, "Mac" is more common in Scotland and in Ulster than in the rest of Ireland; furthermore, "Ó" is far less common in Scotland than it is in Ireland. The proper surname for a woman in Irish uses the feminine prefix nic (meaning daughter) in place of mac. Thus a boy may be called Mac Domhnaill whereas his sister would be called Nic Dhomhnaill or Ní Dhomhnaill – the insertion of 'h' follows the female prefix in the case of most consonants (bar H, L, N, R, & T). A