chaplain (n.)
mid-14c., "minister of a chapel," from Old French chapelein "clergyman" (Modern French chapelain), from Medieval Latin cappellanus "clergyman," originally "custodian of St. Martin's cloak" (see chapel). Replaced Old English capellane (from the same Medieval Latin source) "clergyman who conducts private religious services," originally in great households, later in military regiments, prisons, etc.