Cognomen

The Cognomen, (Latin) was generally the third name a Roman citizen might have in what could be up to a four name naming convention. While not a family name, the cognomen was regularly passed from father to son as a name that said something about the family in a similar way to how the agnomen said somthing about the individual. Classic choices were towns or trades, cultural backgrounds, physical traits etc.

Examples

• If someone had Gaulish ancestory and still identified as such, so they might add galli or a derivative thereof onto the family name.
• Octavian later Augustus Caesar prior to his adoption by Julius Caesar usded the cognomen of Thurinus indicating a family connection the township of Turi in Apulia located in southern Italy.

• similarly the Dutch and Germans regularly have names of van and von to indicate where the family is from.

• a family trait might be red hair or the likes.

• the name of a god the family acknowledged could be used.

• an industry the family worked our founded might be added such as the common English cognomens of:

• Archer
• Cartwright (cart-builder)
• Copper (barrel maker)
• Cutler (knife-maker)
• Fletcher
• Fuller (soap maker / cloth-cleaner and thickener)
• Mason
• Parker (park/estate grounds-keeper)
• Saddler
• Slater (slate-roofer)
• Sawyer (timber cutter)
• Smith (blacksmith)
• Thatcher
• Taylor
• Tiler
• Weaver

But ultimately the cognomen could be anything the family wished that helped describe themselves. But because trades and townships or even family traits passed through generations the cognomen was generally passed from father to son.

Of such the best commonly known example would be that of Gaius Julius Caesar manifesting the:

• praenomen of Gaius being his 'first name'
• nomen of Julius bing his 'family name'
• cognomen of Caesar indicating a denoting a cut (of a sword, knife or spear) making it a fitting cognomen that continued its use accross the successors of the Emperorship while not implying any genetic heritage but maintaining a consistent convention, a heritage and lineage nonetheless.
• agnomen, in this case Julius Caesar never had a personal 'nick-name' attached

As such the cognomen is best thought of as extra information that the family wanted to declare about themselves.

Etymology

Nomen, Latin, literally translated "Name" but in light of the praenomen, the nomen should be considered as a family name. See also agnomen.

Cognitus, Latin, literally translated "the act of getting to know or become aquainted with".

Thereby the cognomen should be considered as a name by which one helps identify the family: a meaningful addition to the family name.