instalmentyoudaoicibaDictYouDict[instalment 词源字典]
"A sum of money due as one of several equal payments for something, spread over an agreed period of time", Mid 18th century (denoting the arrangement of payment by instalments): alteration of obsolete estalment (probably by association with installation), from Anglo-Norman French estalement, from Old French estaler 'to fix'.[instalment etymology, instalment origin, 英语词源]