The surname originated as a patronym, however it no longer refers to the actual name of the bearer's father.

The form of Ó Cadhla for married females is Bean Uí Chadhla, which translates into English as "wife of Ó Cadhla"; this surname can also be represented in the contracted form Uí Chadhla.

[2] According to the early 20th century Irish etymologist Patrick Woulfe, Ó Cadhla has been Anglicised variously as Kiely, Keily, Kealy, Kieley,Keely, Keeley, Kelly, and Quealy.

[1] According to the Irish late 19th century genealogist John O'Hart, the surnames O'Cawley, MacCawley, and Cawley are also Anglicised forms.

Woulfe noted that descendants of both families lived in the Irish provinces of Connacht and Munster.