Yiddish (ייִדיש yidish; literally, Jewish) is a language spoken by Ashkenazi Jews. It is a branch of Old High German, with many loan words from other European languages and from Hebrew. Yiddish is written in the Hebrew alphabet. When the modern nation of Israel was first created in 1948 they chose between Yiddish and Hebrew as their state language. Hebrew won out.
American English has a lot of loanwords from Yiddish, for example bagel, kvetch, borscht, chutzpah, to name just a few. Yiddish was also spoken by many Jewish American comedians, like the Three Stooges and the Marx Brothers. This is used by these comedians as humorous "gibberish" when assuming another identity.
Some Yiddish songs have been introduced successfully into American culture, the most popular being "Bei Mir Bist Du Shein".
The Galut (exile) of the Jews by the Roman Titus after the destruction of the Second Temple in 70 A.D. They were triumphantly displayed in Rome and dispersed in the lands along the Rhine Valley known in the Hebrew tongue as Ashkenaz - which is known now as Germany. There they learned the language of the land which developed into Modern German. The Jews called their language, the early stage of German, Yiddish. From the Rhine, many of the "Ashkenazis" moved (were moved) to Eastern Europe, many fleeing from there, to America, to Israel, to Latin America, etc. learning new languages, but also speaking their old language, not Hebrew, but Yiddish. This, with the common religion, enabled the fostering of unity and brotherhood