Yiddish was at one time the international language of Ashkenazic Jews (the Jews of Central and Eastern Europe and their descendants). A hybrid of Hebrew and medieval German, Yiddish takes about three-quarters of its vocabulary from German, but borrows words liberally from Hebrew and many other languages from the many lands where Ashkenazic Jews have lived. It has a grammatical structure all its own, and is written in an alphabet based onHebrew characters. Scholars and universities classify Yiddish as a Germanic language, though some have questioned that classification.
At its height less than a century ago, Yiddish was understood by an estimated 11 million of the world's 18 million Jews, and many of them spoke Yiddish as their primary language. Yiddish has fallen on hard times, a victim of both assimilation and murder. Today, less than a quarter of a million people in the United States speak Yiddish, about half of them in New York. Most Jews know only a smattering of Yiddish words, and most of those words are unsuitable for polite company. But in recent years, Yiddish has experienced a resurgence and is now being taught at many universities. There are even Yiddish Studies departments at Columbia and Oxford, among others, and many Jewish communities provide classes to learn Yiddish. Many Jews today want to regain touch with their heritage through this nearly-lost language.
Yiddish is referred to as "mame loshn" ("loshn" rhymes with "caution"), which means "mother tongue," although it is not entirely clear whether this is a term of affection or derision. Mame loshn was the language of women and children, to be contrasted with loshn koydesh, the holy tongue of Hebrew that was studied only by men. (And before the feminists start grinding their axes, let me point out that most gentile women and many gentile men in that time and place could not read or write at all, while most Jewish women could at least read and write Yiddish).
The word "Yiddish" is the Yiddish word for "Jewish," so it is technically correct to refer to the Yiddish language as "Jewish" (though it is never correct to refer to Hebrew as "Jewish"). At the turn of the century, American Jews routinely referred to the Yiddish language as "Jewish," and one of my elderly aunts continues to do so. However, that usage has become unfashionable in recent years and people are likely to think you are either ignorant or bigoted if you refer to any language as "Jewish." Likewise, the Yiddish word "Yid" simply means "Jew" and is not offensive if used while speaking Yiddish or in a conversation liberally sprinkled with Yiddish terms, but I wouldn't recommend using the word in English because it has been used as an offensive term for far too long.
From the web page Judism 101
I hope to advance my understanding of this culture as I read the wonderful works in The Yale Digital Yiddish Library.
In her editing of the collection The Cross and Other Jewish Stories of Lamed Shapiro Leah Garrett divides the stories into three groups, one of the sections is devoted to stories set in America. Lamed Shapiro was very much a "stranger in a strange land" as he tried to figure out a way to live in America. Many speakers of Yiddish ("Yiddish" means "Jewish" in the Yiddish language) settled in New York City upon immigration. "New Yorkish" does a marvelous job of letting us see how it might have felt for Shapiro, an unmarried man, to walk the streets of NYC. There is an old line from a song by Jim Morrison, "Women are wicked when you are alone". We see how the truth of this shapes the narrator's perceptions as he meets, goes out with, and sleeps with a waitress in a diner, all in one day. As he enters the diner, the narrator wonders about the ethnic and cultural background of all the customers and his waitress. He does not understand the many nuances of his new home. Of course like any single male immigrant, he wants to meet local women. He begins to chat with the waitress, this conversation is just brilliant. He cannot decide if she is Spanish or a daughter of the American confederacy, which to him means a fallen aristocrat. He tries to find boxes in which to put people, things from his old home. As the woman gets ready to leave in the morning, we never really learn how she saw the man, he gives her money. She refuses but she takes when he insists. Seemingly he needs or wants to see her as a prostitute. In this he degrades the woman and himself.