Question
What is the origin of “Shefoch chamascha” that we say at the Seder?
Answer
Shefoch Chamascha is mentioned in one manuscript of the Siddur of R. Amram Gaon, but it’s not mentioned by R. Saadia Gaon or Maimonides, so it probably wasn’t customary in the time of the Geonim. However, it seems to have been adopted (with variations) in all the minhagim. Thus the custom of saying it seems to be about 1000 years old. Possibly it was a reaction against anti-Semitic accusations related to Passover (the blood libel).