'Fitz' definitions:

Definition of 'Fitz'

From: GCIDE

Fitz \Fitz\, n. [OF. fils, filz, fiz, son, F. fils, L. filius. See Filial.] A son; -- used in compound names, to indicate paternity, esp. of the illegitimate sons of kings and princes of the blood; as, Fitzroy, the son of the king; Fitzclarence, the son of the duke of Clarence. [1913 Webster]