Costello (surname)

Costello is an Irish surname.
History.
The Irish surnames Costello, Costelloe, and Costellow are anglicized forms of the Gaelic surname "Mac Oisdealbhaigh", itself a Gaelicized form of an Anglo-Norman name. This was the first example of a Norman family assuming a Gaelic name.
This surname has been mainly borne by a notable Irish family who claimed descent from Jocelyn de Angulo, an Anglo-Norman mercenary who accompanied Richard de Clare to Ireland in 1170 during the Anglo-Norman invasion of Ireland.
An early record of the name in Ireland appears in the 17th century Annals of the Four Masters where the name is mentioned in the entry for the year in 1193: "Inis Clothrann do orgain la macaibh Oisdealb, & la macaibh Conchobhair Maonmaighe." (Inishcloghbran was plundered by the sons of Oisdealb, and the sons of Conor Moinmoy.) The descendants of Oisdealb then became referred to by the family name "Mac Oisdealbhaigh" (son of Oisdealb).
"Oisdealb" or "Ostealv" is sometimes erroneously explained as a Gaelicization of “Jocelyn”, i.e. Jocelyn d'Angulo. But “Ostealv” is more obviously a Gaelic rendering of “Hostilo”, the name of Jocelyn's brother (also known as Hostilio). It is Hostilo's descendants who would bear the surname Mac Oisdealbhaigh (son of Oisdealb).
Costello has also occasionally has been adopted as a pseudonym or stage name by famous people of Italian descent, including Al Costello ("né" Giacomo Costa), Frank Costello ("né" Francesco Castiglia), and Lou Costello ("né" Louis Francis Cristillo). It is also an Italian verb form of "costellare": to adorn with stars.
According to the Ellis Island official passenger search, some people came from Italy and Spain to the U. S. as Costello.