The term "Yevanic" is an artificial creation from the Biblical word Yāwān referring to the Greeks and the lands that the Greeks inhabited. The term is an overextension of the Greek word Ἰωνία (Ionia in English) from the (then) easternmost Greeks to all Greeks.
There are no longer any native speakers of Yevanic, for the following reasons:
The murder of many of the Romaniotes during the Holocaust;
The adoption of the majority languages through assimilation.
The Jews have a place of note in the history of Modern Greek. They were unaffected by Atticism and employed the current colloquial which they transcribed in Hebrew letters. There is a small literature in this Jewish-tinged Greek, which may be termed Yevanic (Hebrew Yevanim "Greeks", lit. "Ionians"); it dates from the early part of the modern period, the most extensive document being a translation of the Pentateuch. In its context, this exceptional cultivation of the vernacular has its analogue in the choice of Hellenistic Greek by the translators of the Septuagint and in the New Testament.