In the United States the family name was originally spelled Worden. Sometimes in early colonial times, the name was spelled with an "E" instead of an "O." It was very common in those days to spell phonetically, generally where a non-Worden was the writer thereof and spelled it as it sounded.
The change to Warden occured in the life of Rypha Earl Worden [circa 1900], again caused by a non-Worden's misspelling of the name.