Yiddish is the language of eastern European, or Ashkenazic Jews. Yiddish is not Hebrew, which remains (with Aramaic) the Jews’ language of prayer and religious ceremonies. Hebrew is the official language of Israel.
Yiddish uses the letters of the Hebrew alphabet; it is written from right to left; its spelling, which has been standardized, is emphatically phonetic.
Perhaps 15 to 20 percent of the vocabulary of Yiddish consists of Hebrew words and phrases – but Yiddish and Hebrew are as different as, say, English and Hungarian. In addition to its quotient of Hebrew words, the vocabulary of Yiddish is adapted from German (70 to 75 percent) and from Polish, Russian, Romanian, Ukrainian, various Slovene dialects, and, within the last century, English.
Yiddish is not a “new” or even a “young ” language, believe it or not. It is older than modern German, which may be said to have begun with Martin Luther’s translation of the Bible, and it is older than modern English, which dates from 1475, according to the Random House Dictionary.
Yiddish is descended from the form of German heard by Jewish settlers from northern France, about a thousand years ago. As Jews settled in towns along the Rhineland, they adopted and adapted the local vernacular. They wrote German with their Hebrew alphabet, phonetically – just as Jews used Hebrew letters to write many other languages. They shunned Latin and its alphabet, for Latin was associated with things Christian, including pogroms.
The Germanic tongue, heavily studded with Hebrew words and phrases (names, holidays, all religious or ritualistic matters), added words from other languages as the Jews traveled. the new linguistic melange took root and flourished in eastern Europe; it became the beloved native tongue of the Ashkenazim – and was never used by, or known to, the Sephardim.
Since Jewish women were not taught Hebrew, the “sacred tongue”, they spoke Yiddish to the children – who, in turn, spoke it to their parents and, later, to their own children. So Yiddish became known as mameloshn, “mother language,” to distinguish it from loshn ha-kodesh, “the sacred language”.
From “The New Joys of Yiddish, by Leo Rosten. Revised by Lawrence Bush