The name "Julia" has no meaning in Irish.The Irish names Síle (Sheila) and Siobhán were 'translated' as Julia in English, although Síle is from the Latin Cecilia and Siobhán from Johanna...
It's originally a surname (last name). The Irish spelling is "Ó Giollagáin," which is a diminuative of the word "giolla" meaning "lad, youth, page, attendant, servant" so "Giollagáin" means...