German: of uncertain origin. Possibly a southern nickname for a clumsy person, from Middle High German talpe, tape ‘paw’. Alternatively it may be a northern topographic name for someone living by a ditch, Middle Low German delf (frequently an element in compound field names in swampy terrain). A third possibility is that it is from an old personal name, cognate with Anglo-Saxon deal ‘proud’, ‘famous’.
Dictionary of American Family Names © Patrick Hanks 2003, 2006.