The name Joslyn has its roots in the Old English and Old French languages, originating in the Middle Ages. It is a feminine form of the male name Joseph, which is derived from the Hebrew name Yosef, meaning "he will add" or "he will increase."

The name Joslyn first appeared in England during the Norman Conquest in the 11th century, when the Norman French introduced their version of the name Joseline to the region. Over time, this spelling evolved into various forms, including Joslyn, Joslyne, and Joseline.

One of the earliest recorded instances of the name Joslyn can be found in the Domesday Book, a comprehensive survey of England compiled in 1086 by order of William the Conqueror. In this document, a landowner named Joselyn is mentioned, indicating the name's presence in the region at that time.

In the 13th century, Joslyn appeared in the religious text "The Life of St. Margaret of Antioch," where a character named Joslyn was referenced. This early literary mention further solidified the name's place in English culture and literature.

Notable historical figures who bore the name Joslyn include Joslyn of Edingley, a 13th-century English noblewoman who was a benefactor to religious institutions. Another famous bearer of the name was Joslyn Lay, a 15th-century English poet and author known for her work "The Prophecy of Joslyn."

In the 16th century, Joslyn Pearce, an English merchant and explorer, gained recognition for her travels to the New World and her documentation of the indigenous peoples she encountered. Additionally, Joslyn Carr, a 17th-century English Puritan leader, played a significant role in the establishment of religious communities in the American colonies.

During the 18th century, Joslyn Hampden, an English aristocrat and philanthropist, was renowned for her charitable works and advocacy for social reform. Joslyn Elliot, a Scottish writer and poet born in 1796, also contributed to the literary landscape of her time with her published works.

Throughout history, the name Joslyn has carried a sense of elegance, grace, and refinement, reflecting its origins in the noble and literary circles of medieval England and France.