It is in Chapter/Paragraph 30 of Book 1, http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Dionysius_of_Halicarnassus/1B*.html.
thx
"For this reason, therefore, I am persuaded that the Pelasgians are a different people from the Tyrrhenians. And I do not believe, either, that the Tyrrhenians were a colony of the Lydians; for they do not use the same language as the latter, nor can it be alleged that, though they no longer speak a similar tongue, they still retain some other indications of their mother country. For they neither worship the same gods as the Lydians nor make use of similar laws or institutions, but in these very respects they differ more from the Lydians than from the Pelasgians. Indeed, those probably come nearest to the truth who declare that the nation migrated from nowhere else, but was native to the country, since it is found to be a very ancient nation and to agree with no other either in its language or in its manner of living. And there is no reason why the Greeks should not have called them by this name, both from their living in towers and from the name of one of their rulers. The Romans, however, give them other names: from the country they once inhabited, named Etruria, they call them Etruscans, and from their knowledge of the ceremonies relating to divine worship, in which they excel others, they now call them, rather inaccurately, Tusci, but formerly, with the same accuracy as the Greeks, they called them Thyoscoï. Their own name for themselves, however, is the same as that of one of their leaders, Rasenna. In another book I shall show what cities the Tyrrhenians founded, what forms of government they established, how great power they acquired, what memorable achievements they performed, and what fortunes attended them."
Dionysius of Halicarnassus, "Roman Antiquities" , Book I, Section 30