I was told that it was anglesized when the first Sizer, Anthony Sizer left France for the island of Tersira (sp.)? before going to ( I think) Boston. The name had been "DeDesieur", or DeZesieur", or something similar. I did actually see a paper with family ancestry about 30 years ago. Sorry I can't spell the French names. Our family branch is basically a made up name. The name Sizer could have had other origins also, but then the Anthony Sizer ancestors would not be related to them. Anthony had a lot of children. The related Sizers came from him. That's why there aren't many.