quintillion (n.)youdaoicibaDictYouDict[quintillion 词源字典]
1670s, from Latin quintus "the fifth" (see quinque-) + ending from million. Compare billion. In Great Britain, the fifth power of a million (1 followed by 30 zeroes); in U.S. the sixth power of a thousand (1 followed by 18 zeroes).[quintillion etymology, quintillion origin, 英语词源]