Learn how to say Cognomen correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word cognomen:
Word forms: plural cogˈnomens, cogˈnomina (kɑgˈnɑmɪnə Pronunciation for )
the third or family name of an ancient Roman (Ex.: Marcus Tullius Cicero)
any family name; surname; last name
any name; esp., a nickname