In American the meaning of the name Brian is: Strong. Celtic Meaning: The name Brian is a Celtic baby name. In Celtic the meaning of the name Brian is: In use in England since the Middle Ages. Possibly connected with the Irish word for Hill thus 'He ascends.'.Also some texts define it as Strong. 10th century Brian Boru was a high king and great national hero of Ireland.n English the meaning of the name Brian is: Brought to England by the Breton companions of William the Conqueror, this name is originally derived from the Irish word for hill. Welsh Meaning: The name Brian is a Welsh baby name. In Welsh the meaning of the name Brian is: Legendary son of Turenn. 'Strong'.