kägˈnōmən noun
( plural cognomens -ənz ; or cog·nom·i·na -nämənə, -nōm-)
Etymology: Latin, from co- + -gnomen, alteration (influenced by gnoscere to know) of nomen name — more at name , know
1. : surname
having the cognomen Smith
especially : the third of the usual three names of a person among the ancient Romans — compare praenomen , nomen ; see agnomen
2. : name ; especially : a distinguishing nickname or epithet
who gained, and richly earned, the cognomen of Tom-Tom — G.W.Johnson