The name Lynn has its origins in the Celtic language, specifically the Welsh word "llyn" which means "lake" or "pond." It is believed to have originated in the early Middle Ages, around the 5th to 10th centuries AD, in the region now known as Wales and parts of western England.

One of the earliest recorded uses of the name Lynn can be found in the Domesday Book, a survey of land ownership commissioned by William the Conqueror in 1086. The name appears as "Linn" in reference to various locations, likely named after bodies of water.

The name Lynn gained popularity during the Middle Ages, particularly in England and other parts of the British Isles. It was commonly used as a place name, as well as a surname derived from those place names. Over time, it began to be used as a given name for both males and females.

One of the earliest notable individuals with the name Lynn was Lynn Wyche (c. 1510 - c. 1580), an English composer and organist who served under King Henry VIII and Queen Elizabeth I. Another early example was Lynn Regis (fl. 1200s), a medieval Bishop of Norwich in England.

In the 16th century, Lynn Bradshaw (c. 1545 - 1619) was a prominent English merchant and politician who served as Lord Mayor of London in 1598. During the same period, Lynn Thorton (c. 1570 - 1629) was an English poet and playwright known for her religious works.

In the 18th century, Lynn Townsend (1735 - 1795) was a British soldier and explorer who is credited with being one of the first Europeans to explore the interior of Australia.

As the name Lynn became more popular, it began to be used more frequently as a feminine given name, particularly in English-speaking countries. However, it has also been used as a masculine name in some cultures and time periods.