can someone help me with my understanding of a new word that i saw today, "cognomen"?

Atomica defines it as:

A name, especially a descriptive nickname or epithet acquired through usage over a period of time.

would anyone be willing to cite examples of how you'd use it in conversation? are our AWAD nicknames (well, the descriptive ones, at least, as in AnnaStrophic, belligerentyouth etc) considered cognominal?

TIA

~b