 Collatinus was the son of Arruns Tarquinius, better known as "Egerius", a nephew of Lucius Tarquinius Priscus, the fifth King of Rome.Through an accident, Arruns had been born into poverty, but when his uncle subdued the Latin town of Collatia, he was placed in command of the Roman garrison there.The surname "Collatinus" was derived from this town.