The name Kierstyn is a modern variant of the Scottish name Kirstyn, which itself is derived from the ancient Norse name Kristin or Christina. This name has its origins in the Greek word "Christos," meaning "anointed one" or "follower of Christ." It is believed to have emerged around the 4th century CE as a name for Christian converts.

The earliest known use of the name Kristin can be traced back to the 9th century CE in Scandinavia, where it was popularized by the spread of Christianity in the region. Over time, the name evolved into various spellings, including Kirsten, Kirstyn, and eventually, Kierstyn.

One of the earliest recorded individuals with the name Kierstyn was Kierstyn of Wessex, a 10th-century Anglo-Saxon noblewoman who served as an advisor to King Edward the Elder. In the 12th century, Kierstyn of Northumbria was a renowned scholar and author who wrote extensively on theology and philosophy.

During the Middle Ages, the name Kierstyn gained popularity across Europe, particularly in regions with strong Christian influences. Kierstyn of Cologne, a 13th-century mystic and nun, is remembered for her writings on spiritual contemplation and her devotion to charitable works.

In the 16th century, Kierstyn Grimmelshausen, a German novelist and playwright, gained fame for her satirical works that criticized the social and political climate of the time. Around the same period, Kierstyn Dubois, a French explorer and navigator, became renowned for her expeditions to the Americas and her contributions to cartography.

As the name spread across different cultures and languages, variations in spelling and pronunciation emerged. The modern spelling of Kierstyn is believed to have originated in the 19th century, possibly as an attempt to differentiate it from the more common spellings of Kirsten or Kristen.