Answer:
   
   The word "anti-Semitism" was coined in Germany in 1879 by Wilhelm Marr
   as a more euphonious way of saying "Judenhass" (Jew-hatred), and has
   always meant exactly that. Its antonym, "Semitism" connoted a positive
   attitude toward the Jewish people. The word has become too sanitized
   and too easily misunderstood, which is exactly what Marr tried to
   accomplish with the word's creation.
   
   According to a (now discredited) nineteenth century theory that held
   that racial groups and linguistic groups coincide, Semites are natives
   of a group of Middle Eastern nations that are closely related in
   ethnicity, culture and language. Under this theory, the modern day
   Semites would be the Jews and Arabs. In ancient times, the Assyrians,
   Canaanites, Carthaginians, Aramaeans and Akkadians (one of the
   ancestors of the ancient Babylonians) were also counted among the
   Semitic nations. It should be noted that many of these groups
   contributed much to the development of modern culture, in particular
   the Phoenicians (Semitic seafarers including Canaanites, Aramaeans and
   northern Israelites), the Babylonians, as well as the Arabs and Jews.
   
   One theory that has been voiced among the practitioners of ancient
   history is that these groups emerged from a common home in Arabia
   during the early Sumerian period. More likely, they were descended
   from various waves of people who entered the Middle East, only the
   last of which brought the Semitic languages. Like the Babylonian king
   Hammurabi, Abraham appears to have been an "Amurru" or West Semite, a
   group that spread out from the Levant to as far east as Ur and
   Babylon. Hebrew and Aramaic are both West Semitic languages.
   
   The modern day "Semites" all claim to trace their ancestry to Noah's
   son, Shem, from whom they take their name.
   
   Given that the theory of "semites" and non-"semites" is now
   discredited, the preferred term to use is "Antisemitism", which has a
   general connotation of "anti-Jewish". When written in this fashion, it
   helps to eliminate the confusion with the discredited theory. (The use
   of the non-hyphenated form is a suggestion of the distinguished
   historian James Parkes). Emil Fackenheim, the Jewish philosopher, has
   also adopted this spelling, explaining "... the spelling ought to be
   antisemitism without the hyphen, dispelling the notion that there is
   an entity 'Semitism' which 'anti-Semitism' opposes" (Emil Fackenheim,
   "Post-Holocaust Anti-Jewishness, Jewish Identity and the Centrality of
   Israel," in World Jewry and the State of Israel, ed. Moshe Davis, p.
   11, n. 2).