The name Kayleen is of Irish origin, derived from the Gaelic name Caitlín, which is a diminutive form of the name Caitríona. Caitríona itself is derived from the ancient Irish name Cathair, meaning "battle" or "contention." The earliest recorded use of the name Kayleen dates back to the late 19th century.

The name Kayleen has its roots in Celtic mythology and folklore. It is believed to have been associated with the warrior goddess Cathbhuaidh, who was revered for her strength and courage in battle. The name was particularly popular among Irish families who valued these qualities in their daughters.

In ancient Irish texts, such as the Annals of Ulster and the Annals of the Four Masters, there are mentions of women bearing similar names like Caitlín and Caitríona. However, the specific spelling "Kayleen" is a more modern variation that emerged in the late 19th and early 20th centuries.

One of the earliest recorded individuals with the name Kayleen was Kayleen Byrne, an Irish-American actress born in 1888. She appeared in several Broadway productions and silent films during the early 20th century. Another notable Kayleen was Kayleen Thompson, an Australian novelist and poet born in 1926, who gained recognition for her works exploring themes of identity and cultural heritage.

In the realm of sports, Kayleen Pritchard, a Canadian figure skater born in 1942, represented Canada at the 1960 Winter Olympics in Squaw Valley, California. Kayleen Conaghan, an Irish golfer born in 1967, won the Ladies European Tour Order of Merit in 1991.

Additionally, Kayleen Halko, an American poet and writer born in 1962, has gained acclaim for her collections exploring themes of feminism, nature, and spirituality. Her works include "The Breath Between Us" and "The Flower of Awakening."

Throughout history, the name Kayleen has been associated with strength, resilience, and a connection to one's cultural roots. While its origins lie in ancient Celtic traditions, it has evolved to become a name embraced by families across various cultures and backgrounds.