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
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
In the more ancient Greek names the name of the clan was very frequently added in an adjective form to that of the individual; while, conversely, Roman scholars were aware that their ancestors bore originally only one name, the later -praenomen-. But while in Greece the adjectival clan-name early disappeared, it became, among the Italians generally and not merely among the Romans, the principal name; and the distinctive individual name, the -praenomen-, became subordinate. It seems as if the small and ever diminishing number and the meaningless character of the Italian, and particularly of the Roman, individual names, compared with the luxuriant and poetical fulness of those of the Greeks, were intended to illustrate the truth that it was characteristic of the one nation to reduce all to a level, of the other to promote the free development of personality. The association in communities of families under patriarchal chiefs, which we may conceive to have prevailed in the Graeco-Italian period, may appear different enough from the later forms of Italian and Greek polities; yet it must have already contained the germs out of which the future laws of both nations were moulded.
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Reference address : https://www.ellopos.net/elpenor/rome/1-02-earliest-migrations-italy.asp?pg=23