The Collaborative International Dictionary of English v.0.48:

nickname \nick"name`\, n. [OE. ekename surname, hence, a
   nickname, an ekename being understood as a nekename,
   influenced also by E. nick, v. See Eke, and Name.]
   A name given in affectionate familiarity, sportive
   familiarity, contempt, or derision; a familiar or an
   opprobrious appellation; as, Nicholas's nickname is Nick.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Nickname \Nick"name`\, v. t. [imp. & p. p. Nicknamed; p. pr. &
   vb. n. Nicknaming.]
   To give a nickname to; to call by a nickname.
   [1913 Webster]

         You nickname virtue; vice you should have spoke.
                                                  --Shak.
   [1913 Webster]

         I altogether disclaim what has been nicknamed the
         doctrine of finality.                    --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nickname
    n 1: a familiar name for a person (often a shortened version of
         a person's given name); "Joe's mother would not use his
         nickname and always called him Joseph"; "Henry's nickname
         was Slim" [syn: nickname, moniker, cognomen,
         sobriquet, soubriquet, byname]
    2: a descriptive name for a place or thing; "the nickname for
       the U.S. Constitution is `Old Ironsides'"
    v 1: give a nickname to [syn: dub, nickname]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "nickname":
   affectionate name, agnomen, appellation, appellative, baptize,
   byname, byword, call, christen, cognomen, define, denominate,
   denomination, designate, diminutive, dub, entitle, epithet,
   first name, handle, hypocoristic, identify, label, moniker, name,
   nominate, pet name, sobriquet, specify, style, tag, term, title