Dionysius of Halicarnassus, Roman Antiquities 1.20:
They made a treaty with the Pelasgians and, separating their lands, gave to them the areas around the sacred lake, in which most of the area was marsh, and which are now called in accordance with the old turn of dialect is called Velia. It was the custom among the ancient Greeks in many cases to place the syllable ‘ou’, written in one letter, before words which began with vowels. This was like a gamma with two horizontal lines yoked onto one upright one, as in Ϝελένη, Ϝάναξ, Ϝοῖκος, Ϝαὴρ and many other words of this sort.
σπένδονταί τε δὴ πρὸς τοὺς Πελασγοὺς καὶ διδόασιν αὐτοῖς χωρία τῆς ἑαυτῶν ἀποδασάμενοι τὰ περὶ τὴν ἱερὰν λίμνην, ἐν οἷς ἦν τὰ πολλὰ ἑλώδη, ἃ νῦν κατὰ τὸν ἀρχαῖον τῆς διαλέκτου τρόπον Οὐέλια ὀνομάζεται. σύνηθες γὰρ ἦν τοῖς ἀρχαίοις ῞Ελλησιν ὡς τὰ πολλὰ προτιθέναι τῶν ὀνομάτων, ὁπόσων αἱ ἀρχαὶ ἀπὸ φωνηέντων ἐγίνοντο, τὴν ου συλλαβὴν ἑνὶ στοιχείῳ γραφομένην. τοῦτο δ’ ἦν ὥσπερ γάμμα διτταῖς ἐπὶ μίαν ὀρθὴν ἐπιζευγνύμενον ταῖς πλαγίοις, ὡς Ϝελένη καὶ Ϝάναξ καὶ Ϝοῖκος καὶ Ϝαὴρ καὶ πολλὰ τοιαῦτα.