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.”
2.
a familiar form of a proper name, as Jim for James and Peg for Margaret.
1440, misdivision of ekename (c.1300), an eke name, lit. "an additional name," from O.E. eaca "an increase," related to eacian "to increase" (see eke).