Source : Webster's Revised Unabridged Dictionary (1913)

Polyptoton \Pol`yp*to"ton\, n. [L., fr. Gr. ? having, or being
   in, many cases; poly`s many + ? case.] (Rhet.)
   A figure by which a word is repeated in different forms,
   cases, numbers, genders, etc., as in Tennyson's line, -- ``My
   own heart's heart, and ownest own, farewell.''

Source : WordNet®

polyptoton
     n : repetition of a word in a different case or inflection in
         the same sentence; "My own heart's heart"