a name added to or substituted for the proper name of a person, place, etc., as in affection, ridicule, or familiarity

He has always loathed his nickname of Whizzer.

a familiar form of a proper name, as Jim for James and Peg for Margaret.

to give a nickname to (a person, town, etc.); call by a nickname.

Archaic . to call by an incorrect or improper name; misname.

noun

appellation , byname , byword , denomination , diminutive , epithet , familiar name , handle * , label , moniker , pet name * , sobriquet , style , tag * , appellative , cognomen , designation , tag , title , agnomen , andy , handle , hypocorism , hypocoristic , len