early 15c., "a cleansing from impurity," from Latin expurgationem (nominative expurgatio), noun of action from past participle stem of expurgare "to cleanse out, purge, purify; clear from censure, vindicate, justify," from ex- "out" (see ex-) + purgare "to purge" (see purge, v.). Sense of "a removal of objectionable passages from a literary work" first recorded in English 1610s. Related: Expurgatory.