"Variant of O'Neill"
The name Oneil is commonly a male name.
Oneil is an English-language spelling of the Irish surname O'Neill with the apostrophe dropped. The surname is built from the Irish prefix O, meaning descendant of, attached to the personal name Niall. As a boys' given name it belongs to the wider group of Irish surnames used as first names in English-speaking countries.
The pronunciation of Oneil is oh-NEEL.