Source : Webster's Revised Unabridged Dictionary (1913)

Praenomen \Pr[ae]*no"men\, n.; pl. {Pr[ae]nomina}. [L., fr. prae
   before + nomen name.] (Rom. Antiq.)
   The first name of a person, by which individuals of the same
   family were distinguished, answering to our Christian name,
   as Caius, Lucius, Marcus, etc.

Source : WordNet®

praenomen
     n : the first name of a citizen of ancient Rome
     [also: {praenomina} (pl)]