infiltration (n.)youdaoicibaDictYouDict[infiltration 词源字典]
early 15c., "a knitting together," noun of action from infiltrate. In physics, from 1796. Figurative sense of "a passing into" (anything immaterial) is from 1840; military sense of "stealthy penetration of enemy lines" dates from 1930.[infiltration etymology, infiltration origin, 英语词源]