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]