The Collaborative International Dictionary of English v.0.48:

Mirza \Mir"za\, n. [Per. m[imac]rz[=a], abbrev. fr.
   m[imac]rz[=a]deh son of the prince; m[imac]r prince (Ar.
   am[imac]r, em[imac]r) + z[=a]deh son.]
   The common title of honor in Persia, prefixed to the surname
   of an individual. When appended to the surname, it signifies
   Prince.
   [1913 Webster]