From Old English. eaca “an increase,” related to eacian “to increase”.

Here we go ……

I don’t know were it really comes from but let me try and say that a “nickname” is a descriptive name added to or replacing the actual name of a person, place, or thing.

A familiar or shortened form of a proper name.

tr.v., -named, -nam·ing, -names.

To give a nickname to.

Archaic. To call by an incorrect name; misname.

[Middle English neke name, from a neke name, alteration of an eke name : eke, addition (from Old English ēaca) + name, name; see name.]

nicknamer nick’nam’er n.

Hope this could help

Take Care

Nickname is derived from “ekename” meaning “an additional name.”