c. 1300, "summons, written notice to appear," from Old French citation or directly from Latin citationem (nominative citatio) "a command," noun of action from past participle stem of citare "to summon, urge, call; put in sudden motion, call forward; rouse, excite" (see cite).
Meaning "passage cited, quotation" is from 1540s; meaning "act of citing or quoting a passage from a book, etc." is from 1650s; in law, especially "a reference to decided cases or statutes." From 1918 as "a mention in an official dispatch."