| Definition -
(1) Substituting a title or epithet for a proper noun (e.g. calling Bruce Springsteen The Boss).
(2) Using a proper noun to express a general idea (e.g. calling a celebrity train-wreck a Britney Spears).
Etymology - The word derives from the Greek antonomazein, to name differently (from anti, instead + onomazein, to name).
Oxford English Dictionary - Its first citation is from 1589:
"Antonomasia, or the Surnamer, as he that would say:
not king Philip of Spaine, but the Westerne king."
(Puttenham Eng. Poesie (Arb.) 192)