There are three main hypotheses as to the origins of the Etruscan civilization in the Early Iron Age. Autochthonous development in situ out of the Villanovan culture, as claimed by the Greek historian Dionysius of Halicarnassus who described the Etruscans as indigenous people who had always lived in Etruria. A migration from the Aegean sea, as claimed by a couple of Greek historians: Herodotus, who described them as a group of immigrants from Lydia in Anatolia, and Hellanicus of Lesbos who claimed that the Tyrrhenians were the Pelasgians originally from Thessaly, Greece, who entered Italy at the head of the Adriatic sea.  The third hypotheses is reported by Livy and Pliny the Elder, and puts the Etruscans in the context of the Rhaetian people to the north and other populations living in the Alps.
Source: Etruscan origins – Wikipedia