D defs.my
Entry 2 senses Webster, 1913

Cognomen

· Cog·no·men · IPA /kɒɡˈnoʊ.mən/
01 n. The last of the three names of a person among the ancient Romans, denoting his house or family.
  1. 1.
    The last of the three names of a person among the ancient Romans, denoting his house or family.
  2. 2.
    A surname.(Eng. Law)