Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
COSTELLO
As described in historical dictionaries
Patronymica Britannica (1860)
COSTELLO. Among the many ANorm. settlers in Ireland, temp. Henry II., was Hostilio de Angulo. His descendants were called Mac-Ostello (son of Hostilio) which by still further corruption became Costello.
Origin: Celtic
Region of origin: British Isles
Country of origin: Ireland
Religion of origin: Christian
Language of origin: Gaelic