invocation (n.) Look up invocation at Dictionary.com
late 14c., "petition (to God or a god) for aid or comfort; invocation, prayer;" also "a summoning of evil spirits," from Old French invocacion "appeal, invocation" (12c.), from Latin invocationem (nominative invocatio), noun of action from past participle stem of invocare "to call upon, invoke, appeal to" (see invoke).