The name Alanah is believed to have its origins in the Gaelic language, spoken primarily in Ireland, Scotland, and the Isle of Man. It is thought to be a feminine form of the name Alan, which is derived from the ancient Brittonic Celtic name Alen or Alanus, meaning "little rock" or "handsome."

One of the earliest recorded instances of the name Alanah can be found in the Annals of Ulster, an ancient chronicle of medieval Irish history. The entry from the year 1028 mentions an Irish noblewoman named Alanah, suggesting the name's usage in Ireland during that time period.

In the 12th century, Alanah was the name of a Welsh princess who married Rhys ap Gruffydd, the Lord of Deheubarth in South Wales. This historical figure is mentioned in several medieval Welsh chronicles, solidifying the presence of the name in Celtic cultures.

During the Renaissance period, Alanah Blackwood (1495-1563) was a renowned Scottish herbalist and apothecary. She is credited with publishing one of the earliest books on herbal remedies in the English language, further cementing the name's Scottish heritage.

In the 17th century, Alanah O'Malley (1610-1682) was an Irish pirate queen who commanded a fleet of ships and terrorized the coastlines of Ireland and Scotland. Her fearless exploits earned her a place in maritime history and folklore.

In more recent times, Alanah Rae (1986-) is a Canadian actress and video game journalist, known for her work in the gaming industry and her advocacy for women in the field. Her prominence has contributed to the increased popularity of the name Alanah in North America.

While the name Alanah has its roots in the Celtic cultures of the British Isles, its usage has spread to various parts of the world, including North America, Australia, and parts of Europe. It continues to be a popular choice for parents seeking a unique and historically significant name for their daughters.