If you go to
http://tinyurl.com/44g5zlf, you'll find that the Italian name D'Este has been proposed as the origin of Estes. However, you'll also find that the name was variously spelled Eustace, Ewstas, Eustes and the like, and this makes it much more probable that Estes is an alteration of Eustace (also found as Ewstace, Eustes, Eustis, etc.) whose origin you'll find at
http://www.ancestry.com/facts/Eustace-name-meaning.ashx