Why did Constantius Chlorus decide to become a Flavius?

Question

I have noticed that virtually all Roman emperors after Constantine were called Flavius Something. A quick lookup in wikipedia confirms this and even more:

During the later period of the Empire, the name Flavius frequently descended from one emperor to another, beginning with Constantius, the father of Constantine the Great. The name became so ubiquitous that it was sometimes treated as a praenomen, to the extent of being regularly abbreviated Fl., and it is even described as a praenomen in some sources, although it was never truly used as a personal name. The last emperor to take the name was eastern emperor Constantine IV.

After the name fell into disuse among the Byzantine emperors, it was used as a title of legitimacy among the barbarian rulers of former Roman provinces, such as Spain, where the Visigoths and their Spanish successors used the title ″Emperor of All Spain″, and the kings of the barbarian successor kingdoms of Italy, such as the Ostrogoths and the Lombards also used it, with a special meaning as the ″protector″ of the Italian peoples under Lombard rule.

So, I looked up Chlorus and apparently he started calling himself Flavius when he was appointed Caesar in 293 (wiki again):

At Milan on March 1, 293, Constantius was formally appointed as Maximian’s Caesar. He adopted the names Flavius Valerius and was given command of Gaul, Britannia and possibly Hispania.

But why did he choose specifically Flavius?

A cursory search reveals that in the 3rd century a popular soi-disant name for emperors was Aurelius and that Diocletian called himself Aurelius Valerius (so that explains the Valerius part all right).

Was Constantius trying to be special? Was he claiming some particular affinity to the real Flavian dynasty of the 1st century?

What makes this a bit more weird is that apparently Constantius did have a fabricated genealogy but there was nothing Flavian about it:

Born in Dardania, Constantius was the son of Eutropius, whom the Historia Augusta claimed to be a nobleman from northern Dardania, in the province of Moesia Superior, and Claudia, a niece of the emperors Claudius II and Quintillus. Modern historians suspect this maternal connection to be a genealogical fabrication created by his son Constantine I, and that his family were of humble origins.

But Claudius II's full name was Marcus Aurelius Valerius Claudius Augustus and his brother Quintillus was Marcus Aurelius Claudius Quintillus Augustus (note the weird absence of Valerius). No Flavius there! Of course, if the whole thing was invented after Constantius's own time, retconning it properly might have been too complicated.

Maybe Constantius just liked the sound of the name Flavius?

Answer 1

It is true that Wikipedia says:

At Milan on March 1, 293, Constantius was formally appointed as Maximian’s Caesar.[17] He adopted the names Flavius Valerius1 and was given command of Gaul, Britannia and possibly Hispania.

https://en.wikipedia.org/wiki/Constantius_Chlorus1

Thus Wikipedia seems to claim that Marcus Constantius changed his name to Marcus Flavius Valeriaus Constantius in 293 and presumably to Marcus Flavius Valerius Constantius Augustus in 305.

According to the notes the information about his promotion to caesar comes from:

Birley, Anthony (2005), The Roman Government in Britain, Oxford University Press, ISBN 978-0-19-925237-4, page 382.

And the information about his name comes from:

Southern, Pat. The Roman Empire from Severus to Constantine, Routledge, 2001 page 147.

there are several possibilities:

1) It is very commonly known (or believed or assumed) that Constantius took the names of Flavius and Valerius when appointed Caesar in 293, and thus the Wikipedia contributor didn't see the need to give a specific footnote for Constantius adopting the name Flavius.

2) A statement that Constantius took the names of Flavius and Valerius when appointed Caesar in 293 is in one or both of the two sources cited for that paragraph of the Wikipedia article. Thus the source(s) should give their sources.

3) It is not commonly known (or believed or assumed) that Constantius took the names of Flavius and Valerius when appointed Caesar in 293, and so the Wikipedia contibutor should have seen the need to give a specific footnote for Constantius adopting the name Flavius, but didn't, and it is not in either of the two sources given.

DIR De Imperatoribus Romanus does not discuss Constantius's name.

http://www.roman-emperors.org/chlorus.htm2

One logical place to look would be Jones, A.H.M., Martindale, J.R. The Prosopography of the Later Roman Empire, Vol. I: AD260-395, Cambridge University Press, 1971

One clue is the name of his first wife Flavia Iulia Helena Augusta. He divorced her sometime before 389 to marry Theodora, daughter of Emperor Maximian. She was appointed Augusta by her son Constantine in 325.

https://en.wikipedia.org/wiki/Helena_(empress)3

So when did she get the name Flavia? Was she born Flavia Julia Helena about 248 or 250? Did she became Flavia when she married Constantius about 270? Did she become Flavia only after her son constantine was proclaimed emperor in 306?

Answer 2

Turns out that wiki is misleading on this point (I will try to amend it).

The original name was Flavius Constantius. My reference for this is p. 139 of the following paper.

Salway, Benet. "What's in a Name? A Survey of Roman Onomastic Practice from c. 700 BC to AD 700." Journal of Roman Studies 84 (1994): 124-145.

When in 293 the imperial college was doubled by the recruitment of two Caesars, each to be lieutenant and designated heir to an Augustus, [...] each of the new Caesars adopted the senior Augustus' nomen after their own [...], in conjunction with the praenomen of their immediate superior. So Galerius Maximianus, Diocletian's Caesar, became C. Galerius Valerius Maximianus and Flavius Constantius, Caesar to Maximian, became M. Flavius Valerius Constantius.

So, Constantius was a Flavius to begin with. Probably this means that there is no way to trace his name any further back, as we know next to nothing about his background and family (except that unhelpful probably-fake genealogy).

Salway's paper mentions a soldier by the name Flavius Euclides, by the way.

P.S. The absence of pre-nomen is not a mistake. According to Salway's theory the "New Romans" (i.e. those enfranchised in 212 by Caracalla) did not take to the use of pre-nomen outside of official documents (where most people were called M. Aurelius Something anyway, like our friend Flavius Euclides who was officially listed as M. Aurelius Flavius Euclides in his unit's roster). Read the whole paper for more fun stuff about names.