Literally, “Jewish;” a Pseudo-Language based on German, with many Hebraisms, including Hebrew words, phrases, interjections (such as “Oy Vey!”) and untranslatable manners of expression, inter-mixed to create a kind of uniquely Jewish language. In addition to the German, which is the base language, there are traces of Russian, Polish, Hungarian, Rumanian and just about all of the Northern and Western European languages spoken by the Peoples with whom the Jews lived during one thousand years, more-or-less, of their European “Galut,” or Exile.
Yiddish is not the first Jewish Pseudo-Language. Mainly in the Plain of Spain (get the “My Fair Lady” reference – Ha! Ha!), the Jewish People created “Ladino,” a different form of “Yiddish” developed with a similar admixture of Hebraisms into the base language of Spanish.
Aramaic as well, the language of the Babylonian Talmud, is a form of “Yiddish,” with a heavy admixture of Hebraisms into the similar Semitic language spoken in Babylonia.
While it has been abandoned by large circles of Modern Jews in favor of “Ivrit, the Hebrew Language,” the Classical Language of the Jewish People, and the language adopted officially by the State of Israel, it is maintained and spoken by equally large circles of Modern Jews, mainly of Chassidic Communities. They are waging a strong battle against the corrosive influences of Western Culture, outside and inside of Israel, and they reject certain aspects of the Modern State of Israel.