Abstract: Since the development of historical linguistics, it has been observed that the Ancient Greek language contains a significant number of words with no Indo-European etymology, which have been designated as a Pre-Hellenic substratum in the Indo-European Greek language. These words include toponyms, anthroponyms and divinity names, among other loanwords. The present study enquires into the origins of this substratum in the Ancient Greek language of the 1st millennium BCE. Although mainstream archaeolinguistics argue mainly for an Anatolian origin of this substratum, linguistic evidence will be presented herein for an Eteocretan influence in the formation of a significant part of it. Several examples are provided for well-known cases of proper nouns and other loanwords, along with examination of some linguistic data and, finally, conclusions, concerning the linguistic characteristics of this substratum and of Ancient Greek.