The given name Callen has its origins in the Gaelic language, specifically the Irish and Scottish Gaelic dialects. It is believed to have emerged during the early medieval period, around the 5th to 8th centuries AD. The name is derived from the Irish word "callan," which means "young man" or "boy."

One of the earliest recorded instances of the name Callen can be found in the Annals of Ulster, a chronicle of medieval Irish history. In this text, a person named Callen Mac Scannlain is mentioned as having been involved in a battle in the year 1014 AD. This suggests that the name was in use among the Irish and Scottish Gaelic communities during that time.

Throughout history, there have been several notable individuals who bore the name Callen. One of the most prominent was Callen of Echtra, an Irish hero and warrior who lived in the 6th century AD. He is celebrated in the medieval Irish literary tradition for his bravery and exploits.

Another historical figure with the name Callen was Callen Mulrooney, an Irish poet and bard who lived in the 15th century. His works, which were written in the Gaelic language, are considered important examples of Irish literary heritage.

In the 16th century, there was a Scottish nobleman named Callen MacDonald, who was a member of the powerful Clan Donald and played a role in the conflicts between the Scottish clans and the English crown.

Moving forward to the 19th century, we find Callen Byrne, an Irish artist and painter who was born in 1819 and is renowned for his landscape paintings that captured the beauty of the Irish countryside.

Finally, in the 20th century, there was Callen O'Reilly, an Irish author and playwright who was born in 1905. His works dealt with themes of Irish identity, culture, and the struggles of the working class.

These examples demonstrate that the name Callen has a rich history and has been borne by individuals from various walks of life, including warriors, poets, nobility, artists, and writers, over the course of many centuries.