There are many variations to the spelling for many reasons including because so many people could not read or write. In 1774 I found it spelled Cassie. In 1795 on the land deed it's Carsie. It becomes very confusing because an Andrew Casaday mirgrated in the same pattern as Abraham, but is probably not related because of the different spelling on the same documents. The descendants in Wayne County stated about 35 years ago that Abraham was "Black Dutch" which means he came from Germany. Supposedly the name was slightly changed because of confusion with a pirate by the same name. I have not found any proof of that. I'm sorry, but I do not believe Isaac Newton Casida is a descendant of Abraham. There is too much information to the contrary and no proof. He could be a nephew of Abraham or a descendant of Peter Casida from Ireland, which Andrew above is and has many descendants named Isaac Newton.