allusion (n.) Look up allusion at Dictionary.com
1540s, "metaphor, parable" (a sense now obsolete); 1550s, "word-play, joke;" 1610s as "passing or casual reference," from Latin allusionem (nominative allusio) "a playing with, a reference to," noun of action from past participle stem of alludere "to play, jest, make fun of," from ad "to" (see ad-) + ludere "to play" (see ludicrous). An allusion is never an outright or explicit mention of the person or thing the speaker seems to have in mind.