About the O'Neill surname
The surname O'Neill is associated with a patronymic formation. The O' particle is an old Irish patronymic formation associated with descent. The name therefore belongs to a tradition in which an ancestor's given name gradually became a hereditary surname. The O’ particle in O'Neill is characteristic of many Irish surnames and traditionally refers to descent. In the normalization used for some LAFRANCE searches, the surname is also matched through the form “oneill”; this search variant can be useful when accents, spaces, or punctuation differ.
Pronunciation:
Eou-nil/əʊnil/