The Term "Ashkenazi"

Ashkenaz is another name in Medieval Jewish Literature for Germany.
Ashkenaz was originally the name of a son of Gomer son of Japhet son of Noah.

Genesis 10:
 10 Now these are the records of the generations of Shem, Ham, and Japheth, the sons of Noah; and sons were born to them after the flood.
 2 The sons of Japheth were Gomer and Magog and Madai and Javan and Tubal and Meshech and Tiras. 3 The sons of Gomer were Ashkenaz and Riphath and Togarmah.

It was believed that descendants of Ashkenaz had first dwelt in what is now Turkey and Russia and then moved to Germany, especially the northern part.
 Jews who lived in Germany were referred to by other Jews as "Ashkenazim." The same thing happens today where Jews in one country are named after that country by Jews in another, e.g. Jews in the USA will be referred to as "Americans" by Jews in Israel. The term 'Ashkenaz' may have had an ethnic connotation for the Gentile inhabitants of Germany but it had none for the Jews. When due to the Crusades and other matters the Jews of France and Germany (i.e. Ashkenazim i.e. German born) moved eastward they brought their language (Yiddish) and culture with them. Local Jewish communities, where they existed, were socially dominated by the new "Ashkenazim." Consequently all Jews of Northern Europe became known as "Askenazim." This was to distinguish them from the "Sephardim" of the south and east some of whom in a similar way had once dwelt in Sepharad i.e. in Spain. (Note by Ami Elat: Interestingly, in Eastern Europe, the Sepharadic Jews were called 'Franks', by the Eastern European Jews, perhaps because the post-Roman Frankish Empire included part of northern Spain.)