Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
About fourteen miles up from the mouth of the river Tiber hills of
moderate elevation rise on both banks of the stream, higher on the
right, lower on the left bank. With the latter group there has been
closely associated for at least two thousand five hundred years the
name of the Romans. We are unable, of course, to tell how or when
that name arose; this much only is certain, that in the oldest
form of it known to us the inhabitants of the canton are called not
Romans, but Ramnians (Ramnes); and this shifting of sound, which
frequently occurs in the older period of a language, but fell very
early into abeyance in Latin,(1) is an expressive testimony to the
immemorial antiquity of the name. Its derivation cannot be given with
certainty; possibly "Ramnes" may mean "the people on the stream."
1. A similar change of sound is exhibited in the case of the following
formations, all of them of a very ancient kind: -pars--portio-,
-Mars- -Mors-, -farreum- ancient form for -horreum-, -Fabii- -Fovii-,
-Valerius- -Volesus-, -vacuus- -vacivus-.