Original Gaelic spellings

• Ó Nualláin, Ó Nuallain (Nolan, Nowlan, etc.)
• O hUllacháin (Nolan, Holohan, Hullachan, etc.)
• O hUltacháin (Nolan, etc.)

Intermediate Spellings

• O Nolan
• O Nowlan
• O Nolloghan

Modern-Day Spellings

• Knolan, Knollin, Knowling
• Noalan
• Nolane
• Nolen
• Nollan, Nolland, Nollane, Nollann
• Nolon
• Noolan, Noolane
• Noulan, Nouland
• Noulen
• Nowalan
• Nowlan, Nowland, Nowlands, Nowlane, Nowlen, Nowlon
• Nullon