Complex sentence: This name is however etymologically unrelated to "Brendan"; it is in fact derived from the surname "Brennan", which is an Anglicised form of the Irish "Ó Braonáin".
Split into simpler sentences: This name is however etymologically unrelated to "Brendan". It is in fact derived from the surname "Brennan", which is an Anglicised form of the Irish "Ó Braonáin".