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.
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. [Romaniot were Jews settled in in the Eastern Roman Empire long before its division from its Western counterpart, and they were linguistically assimilated long before leaving the Levant after Adrian’s decree against them and their Religion. As a consequence, they spoke Greek, the language of the overwhelming majority of the populace in the beginning of the Byzantine Era and that of the Greek élit thereafter, unti the fall of the Ottoman Empire. So there was no place for a Yevanitic Language. Had been any attempts to write Greek in Hebrew characters, there were abortive, and never reached the community. Nor there was any reason for Ladino assimilation, since the communities either were geographically apart or had different synagogues, because their liturgies differed greatly. The truth lies on the opposite; Ladino speakers were linguistically assimilated in Greek speaking areas and Ladino use dwindled to elderly jargon by the 50s. The term ‘Yavanitic Language’ is but a coined one.]
There is a small amount of literature in Yevanic dating from the early part of the modern period, the most extensive document being a translation of the Pentateuch. A polyglot edition of the Bible published in Constantinople in 1547 has the Hebrew text in the middle of the page, with a Ladino (Judaeo-Spanish) translation on one side and a Yevanic translation on the other. 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.