Anyway, here's more to the story:
"The first paper appeared in the Independent Journal on 27 October 1787 and was signed Publius, a signature that all subsequent articles bore, for authorship was secret. Publius, the collective pseudonym employed by Hamilton, Madison, and Jay, ultimately produced some 175,000 words in defence of the new federal Constitution. Hamilton chose the pseudonym for what it represented in the history of Rome. Publius Valerius was a Roman hero celebrated for establishing a stable republican government in Rome after Lucius Brutus overthrew Tarquin, the last king of Rome. Plutarch describes Publius as a great lawgiver whose achievements for Rome were equivalent to those of Solon for Greece.
source:http://ezinearticles.com/?Hamilton,-Madison-and-Jay---Publius&id=128217
Plutarch is a good source, but I learned my history of the early Roman Republic from Livy. I love those long speeches that Livy himself must have heard. :)