purgation (n.) Look up purgation at Dictionary.com
late 14c., "purification from sin," also "discharge of waste," from Old French purgacion "a cleansing," medical or spiritual (12c., Modern French purgation) and directly from Latin purgationem (nominative purgatio) "a cleansing, purging," figuratively "an apology, justification," noun of action from past participle stem of purgare (see purge (v.)).