About the O'Reilly surname
The surname O'Reilly is associated with a patronymic formation. The O' particle is an old Irish patronymic formation associated with descent. The surname may originally have expressed descent before becoming fixed as a hereditary family name. The O’ particle in O'Reilly 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 “oreilly”; this search variant can be useful when accents, spaces, or punctuation differ.
Pronunciation:
Eou-raj-li/əʊʁajli/