The name Seanna originates from the Irish Gaelic language and has its roots in ancient Celtic culture. It is a feminine form of the name Sean, which is derived from the Old Irish word "shan" meaning "ancient" or "old."

Seanna is believed to have first appeared as a name in the 5th or 6th century AD, during the early Christian era in Ireland. It was likely used as a name for girls born in Irish monastic communities or among the noble families of the time.

While there are no definitive references to the name Seanna in ancient texts or religious scriptures, it is possible that the name was used in oral traditions or local records that have been lost over time.

One of the earliest recorded examples of the name Seanna can be found in the Irish Annals from the 9th century AD, where a woman named Seanna ingen Áeda is mentioned. However, there are few other documented cases of the name's use until more recent centuries.

Throughout history, several notable individuals have borne the name Seanna. One of the earliest was Seanna Ní Chinnéide (c. 1350 – 1425), an Irish noblewoman and poet who lived during the late medieval period. Another figure was Seanna Nic an Bhaird (c. 1560 – 1630), a Scottish-Irish Gaelic poet and harper from the 16th and 17th centuries.

In more modern times, Seanna Browder (1933 – 2004) was an American actress and dancer who appeared in several Broadway productions and television shows. Seanna Buckman (born 1975) is a contemporary Canadian writer and artist known for her work in children's literature.

Additionally, Seanna Mulholland (born 1979) is a Scottish actress and singer who has performed in various stage productions and television series. These are just a few examples of individuals who have carried the name Seanna throughout history.