There has been a legend in my branch of the Sy family that the name was shortened from "de Saveny" by taking the first and last letters of Saveny. This was documented in a letter written by Vera Sy in 1948. This letter was written to Robert and Gladys Sy. The letter said that the former members of our family were Frenchmen. They belonged to the first Protestants who were called Huguenots. In the seventeenth century they had to flee from France to Germany. At this time they changed their name. This was what she remembered from an old French bible that her husband received from his father. The bible was lost during WWII.
I have traced the family beyond the seventeenth century so I know this legend is not true.