The surname Mullaley has its origins in Ireland, with records dating back to the 16th century. It is believed to be a variant of the Irish Gaelic name Ó Maolalaídh, which means "descendant of the servant of St. Laidhe." The name is derived from the Irish words "maol," meaning "tonsured" or "servant," and "Laidhe," a female saint's name.

The earliest recorded bearer of this surname was Teige O'Mullaley, who lived in County Fermanagh, Ireland, in the late 16th century. The name was also found in the Annals of Ulster, a chronicle of medieval Irish history, which mentions a "Giolla na Naomh O'Mullaley" in the year 1398.

In the 17th century, the Mullaley family was prominent in County Cavan, Ireland, where they held lands around the town of Bailieborough. One notable member of the family was Edmond Mullaley, a Catholic priest and scholar who lived in the late 17th century and wrote extensively on Irish history and literature.

The Mullaley name was also found in other parts of Ireland, such as County Mayo, where a branch of the family settled in the 18th century. One of the earliest recorded individuals with this surname in County Mayo was Patrick Mullaley, who was born around 1740 in the town of Ballina.

Throughout the 19th century, many individuals with the Mullaley surname emigrated from Ireland to various parts of the world, including the United States, Canada, and Australia. One notable figure from this period was James Mullaley, an Irish-born engineer who played a significant role in the construction of the Canadian Pacific Railway in the late 19th century.

Other historical figures with the Mullaley surname include:

1. Thomas Mullaley (1785-1864), an Irish politician and Member of Parliament for County Cavan.
2. John Mullaley (1842-1923), an Irish-American soldier who served in the American Civil War and later became a successful businessman in New York City.
3. Margaret Mullaley (1870-1947), an Irish-born actress and singer who performed on stage in London and New York in the late 19th and early 20th centuries.
4. William Mullaley (1901-1976), an Australian politician and Member of the Legislative Assembly of Western Australia.
5. Michael Mullaley (1929-2003), an Irish-born academic and author who taught at various universities in the United States and wrote extensively on Irish literature and culture.