It can be of several different origins:
MacMullen (Scottish) in Ulster would be Mac Maolain
O'Mullan is Ó Maoláin
O'Mellan (Tyrone) is Ó Mealláin also called 'Mullan'.
The spelling in the question is the correct spelling of the surname Sullivan.
Another answer:
If you are requesting the Irish form of the name: Ó Súilleabháin
Ó Súilleabháin - male version Ní Súilleabháin - female version
In Irish the surname is spelled Ó Súilleabháin.
For a male Ó Súilleabháin;
for a 'maiden name' Ní Shúilleabháin and
for a 'married name' Uí Shúilleabháin is the traditional female usage.
O'Sullivan = Ó Súilleabháin
mac in Irish and Scottish Gaelic.
In the Irish language, deaide.In the Scottish Gaelic language, ......
Liam is in Irish Gaelic already. Pronounced lee-um.
Sullivan or O'Sullivan is an Irish surname. It was originally spelled Ó Súileabháin in the Irish language ("Gaelic"). It is thought to derive from Súldubán (dark-eyed).
In Irish: Pilib.In Scots Gaelic: Filip.
Irish: RoibeardScottish: Raibeart
Nichole
Pádraigín = Irish
Gillian
Scottish Gaelic: Lunnainn. Irish Gaelic: Londain.
In Scottish Gaelic, Steaphag.In Irish Gaelic, Stephanie or Stiofáinín.