The name of the unit means "reliable Flavian legion". Jona Lendering argues that this indicates it was founded in the reign of an emperor named Constantius of the Flavian dynasty, and therefore must have been founded by Constantius II (r. 337–361), the only Flavius Constantius that ruled the Eastern Empire.[1] One alternative explanation is that it originated as a vexillatio (detachment) of Legio I Flavia Gallicana Constantia,[2] founded by Constantius Chlorus and stationed in Armorica in Gaul.[3] Another is that it was originally called Legio IV Galeriana Thebeorum, named after Galerius and renamed by his rivals after his death.[4]
^Scharf, Ralf (2005). Der Dux Mogontiacensis und die Notitia Dignitatum: eine Studie zur spätantiken Grenzverteidigung (in German). Berlin: De Gruyter. pp. 228–229. ISBN978-1-4416-1772-9. OCLC191935869.
^Rolfe, J. C. (1862). Ammianus Marcellinus: Roman History. London: Bohn. There had been assigned for the protection of this city [Singara] two legions, the first Flavian and the first Parthian, and a great body of native troops, as well as a division of auxiliary cavalry which had been shut up in it through the suddenness of the attack made upon it.
^Stoll, Oliver (2001). Römisches Heer und Gesellschaft: gesammelte Beiträge 1991-1999 (in German). Stuttgart: Steiner. pp. 266–267. ISBN3-515-07817-7. OCLC50381071.