Sherrill as a last name is extremely common in Catawba County, NC (Hickory area, north of Charlotte), where they were the pioneering family in the late 1700's. I knew scads of 'em there (including my next-door neighbors). For a message/discussion board on the surname and some historical background, go to www.genforum.com\sherrill\ .
Sorry, no info on its use as a first name. I'd bet on it being a spelling variant of "Cheryl" unless the surname has some presence in your family background.