O’Mullan and all its variants derive from the Gaelic surname O’Maoláin, which dates to before the 10^th century. ‘Maol” means bald or tonsured. So Maoláin refers to a monk or a disciple, or really anyone who shaves their head as a sign of religious devotion. So O’Maolain, in effect, is a surname meaning ‘son of the monk’ or ‘son of the disciple’.

Because it’s a descriptive, it was used by a number of families. There is a line descended from an early king of Connacht, and a Munster line that spells it as Mullane or Mullins. There is a line descended from lowland Scottish migrants who colonized Down and Antrim in the 17th century, but we descend from one of the native Irish family lines using that name in Ulster.

What’s in an ‘O’? 

In Gaelic, the form of a surname varies according to whether its bearer is a man or a woman, and in the case of a married woman, whether or not she chose to adopt her husband’s surname.

• ‘Mc’ or ‘Mac’ indicates ‘a son of”
• ‘O’ indicates ‘a descendant of’
• ‘Ní’ indicates ‘a daughter of’
• ‘Uí’ indicates ‘a wife of’ – but a married woman might choose to retain her ‘Ní’ name after marriage.

Grammar can change the sound of a name when you add a prefix. A son would be called ‘McMullan’ – pronounced just the way you’d expect – but a daughter would be ‘Ní Mhullan’ which is pronounced more like ‘Knee Vullan”.

The Politics of ‘O’

My 2nd great-grandparents and all their children are buried under this tombstone. You’ll see that they sometimes use – and sometimes don’t use – the ‘O’ in front their name. They were all native English speakers so, for them, using the ‘O’ had more to do with politics than language. It could mark you out for trouble, or as trouble.

My second great-grandfather, Daniel, used the ‘O’ at his wedding, but was buried without it. My great-grandfather, Daniel W, was a civil servant and never used the ‘O’ in his lifetime, but was buried by his sons with one, just after partition. They used it or dropped it, depending very much on political climate and social context. It didn’t come into consistent use in my family until 1922, when my grandfather and his siblings migrated to America, just after partition and burying their father.

In the 1980s, while visiting his family’s hometown in Antrim, my father introduced himself as ‘Bob O’Mullan’ and a well-meaning stranger said to him, “Pleasure to meet you, Bob, but you should know it’s a caution not to use the ‘O’ around here.”