From Walsh's History of the Irish Hierarchy, 1854, c. xliv p. 429ff:
Finglass in the barony of Castleknock two miles north of Dublin. According to Archdall this monastery was founded in the early ages ot the Irish Church and probably by St. Patrick himself. One would suppose that the disciples of St. Patrick were required for the wants of the mission nor can it be imagined where postulants for admission to all those establishments could be procured all at once.
Saint Kenicus is called abbot of Finglass. His festival was observed here on the 12th of October. Saint Florentius whose feast is observed on the 21st of January according to Archdall is buried in Finglass.
There is a St. Florentius who was contemporary with St. Germain of Paris who died in 576. Florence was a priest and an Irishman of great reputation and whose memory is revered at Amboise in France. Dagobert, son of Sigebert, king of Austrasia, had been sent when a child to a monastery in Ireland after his father's death A.D. 655 by Grimoald, mayor of the palace. The monastery in which he was placed is said to have been that of Slane. Dagobert remained in Ireland until about the year 670 when he was recalled to his own country and received a part of Austrasia from Childeric II. On the death of Childeric he became sovereign in 674 of all Austrasia by the name of Dagobert II and ruled over that country until he was assassinated in 679. After his return to Austrasia we find some distinguished natives of Ireland, particularly St. Argobast and St. Florentius and who is different it seems from the saint of that name revered in Amboise. Argobast was living in a retired manner at Suraburg when he was raised to the bishopric of Strasburgh about the year 673 by king Dagobert. At Suraburgh, a monastery was erected in honor of St. Argobast. Being a very holy man he is said to have possessed a considerable share of learning and to have written some ecclesiastical tracts. St Argobast died on the 21st of July 679 and was succeeded in the same year by his friend and companion St. Florentius. Florentius took up his abode in the forest of Hasle in Alsace near the place where the river Bruscha flows from the Vosges. Here was founded a monastery either by himself or for him by Dagobert by whom he was greatly esteemed. It is said that he restored her sight and speech to the daughter of that king. While bishop of Strasburgh he founded according to some accounts the monastery of St. Thomas in that city for Scots or Irish. Having governed the see of Strasburgh eight years St. Florentius died on the 7th of November A.D. 687.
A.D. 795 died the abbot Dubhlitter.
A.D. 865 died Robertach bishop and chronographer of Finglass. If Dublin had been a see as early as some pretend it to have been it would be absurd to have a bishop at Clondalkin and another at Finglass. There is a remarkable well at Finglass dedicated to St. Patrick. Tradition affirms that it was formerly celebrated through the miracles wrought there.