Hi there, while there is always more to be said on this topic, you may be interested in this section of our FAQ on Jewish Stereotypes and Persecution Throughout History.

There is a great book about this! David Nirenberg's Anti-Judaism: The Western Tradition. http://www.amazon.com/Anti-Judaism-Western-Tradition-David-Nirenberg/dp/0393347915

He argues that it goes back at least to the Egyptians, and that's not totally clear exactly why it started, but it seems to include some elements of critique/fear of judgement from the Jews different practices (refusing to eat local (nonkosher) food or worship local Gods) and some element of concern that they're not "really from" wherever they live and always have more loyalty to other Jews than to their local neighbors. Those remarks have been very common and recurring over the long history of anti-Judaism.