Members of this gens are first mentioned towards the end of the third century BC, participating on the Roman side during the Second Punic War.
[1] The first of the Decimii appearing in history was from Bovianum, a town of the Samnites, and those Decimii occurring in later times were likely his descendants, who settled at Rome after obtaining Roman citizenship.
[2] The main praenomina of the Decimii at Rome were Gaius, Marcus, and Lucius, the three most abundant names at all periods of Roman history.
The earliest member of this gens to occur in Roman writers bore the praenomen Numerius, a name common among the Oscan-speaking peoples of Italy, but comparatively scarce at Rome.
The only cognomen found among the Decimii of the Republic is Flavus, meaning "golden" or "golden-brown", originally indicating someone with fair hair.