'Polyptoton' definitions:

Definition of 'polyptoton'

noun

Repetition of a word in a different case or inflection in the same sentence; "My own heart's heart"

From: GCIDE

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." [1913 Webster]