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]