exception Look up exception at Dictionary.com
late 14c., from Anglo-Fr. excepcioun, Fr. exception, from L. exceptionem, noun of action from excipere (see except). The exception that proves the rule is from law: exceptio probat regulam in casibus non exceptis, "the exception proves the rule in cases not excepted;" exception here being "action of excepting" someone or something from the rule in question, not the person or thing that is excepted. Related: Exceptional (1846).