Searbhreathach is the Irish language name meaning "judicious", when translated into English the name Justin, has been used in its stead, which is derived from the Latin Justinus.
The name originally appeared in the Annals of the Four Masters, a document from 1616. Saorbhreathach is listed as Lord of Eoghanacht, one of the seats of the ancient kingdom of Eóganachta in what is now part of Republic of Ireland.
References
Searbhreathach Wikipedia(Text) CC BY-SA