Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
GILLESPIE
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
The Gaelic for Archibald, from Gille, a youth or servant, and speach, a word expressive of quickness and sharpness in battle; spuaic, Gaelic, to break the head, to knock.
Patronymica Britannica (1860)
GILLESPIE. A corruption of GilleEsjniauj, Gaelic, "the Servant of the Bishop." It was originally spelt Gillespie, and frequentlj emploj'ed in the Highlands as a Christian name.
Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
Surname type: From name of parent
Origin: Celtic
Region of origin: British Isles
Country of origin: Ireland
Religion of origin: Christian
Language of origin: Gaelic