The name Finnian is derived from the Irish Gaelic name Finnian, which is a diminutive form of the name Finn. The name Finn is believed to come from the Old Irish word "finn," meaning "fair" or "white." This suggests that the name Finnian was originally used to describe someone with fair hair or a pale complexion.

The earliest recorded use of the name Finnian dates back to the 5th century AD, when it was borne by several Irish saints and scholars. One of the most notable was Saint Finnian of Clonard (470-549 AD), who founded the renowned monastic school of Clonard in County Meath, Ireland. This school produced many of the great missionaries and scholars who helped spread Christianity throughout Europe during the Middle Ages.

Another notable figure was Saint Finnian of Moville (495-589 AD), who founded the monastery of Moville in County Down, Northern Ireland. He is credited with introducing the tradition of the Lenten fast to Ireland and is also believed to have been the first Irish saint to make a pilgrimage to Rome.

In the 7th century, the name Finnian was borne by Finnian of Bright (590-635 AD), an Irish monk and scholar who founded the monastery of Maghbile in County Down. He was renowned for his knowledge of the Scriptures and his ability to interpret them.

The name Finnian also appears in Irish folklore and mythology. In the Fenian Cycle of Irish mythology, one of the principal characters is Finn MacCool (Finn mac Cumaill), a legendary warrior and leader of the Fianna, a band of elite mercenary soldiers.

Other notable historical figures with the name Finnian include Finnian of Clonmore (c.700-c.790 AD), an Irish monk and abbot who founded the monastery of Clonmore in County Carlow, Ireland. Finnian of Quentovic (c.810-c.876 AD) was a Flemish monk and abbot who played a significant role in the development of the Benedictine monastic tradition in Flanders.