Webster's 1913 Dictionary
O'
O' O', Etym: [Ir. of a descendant. ]
Defn: A prefix to Irish family names, which signifies grandson or descendant of, and is a character of dignity; as, O'Neil, O'Carrol.
O'
O' O', prep.
Defn: A shortened form of of or on. "At the turning o' the tide. " Shak.
New American Oxford Dictionary
O'
O' ▶prefix in Irish patronymic names such as O'Neill . ORIGIN mid 18th cent.: from Irish ó, ua ‘descendant. ’
o'
o' |ə, ō ə | ▶preposition short for of, used to represent an informal pronunciation: a cup o' coffee.
Oxford Dictionary
O'
O' |əʊ, ə | ▶prefix in Irish patronymic names such as O'Neill . ORIGIN mid 18th cent.: from Irish ó, ua ‘descendant ’.
o'
o' |əʊ, ə | ▶preposition short for of, used to represent an informal pronunciation: a cup o' coffee.
Duden Dictionary
O'
O' Eigenname Bestandteil irischer Namen (z. B. O'Neill )
Sanseido Wisdom Dictionary
O'
O' /oʊ /接頭辞 …の息子 (!アイルランド系の姓に付けられる; →Mac- , Fitz- ) ▸ O 'Neill オニール .
o'
o' /ə /前置詞 1 ｟くだけて ｠＝of 1 (!発音つづり; →o'clock ) .2 ｟文 ｠＝on .
The Wordsmith Dictionary