interloper: [16] An interloper is literally someone who ‘runs between’. The word was coined in English, but based on Dutch loper, a derivative of lopen ‘run’ (to which English leap is related). It originally denoted someone who engaged in trade without authorization, and only in the 17th century took on its present-day meaning ‘interfering outsider’. => leap[interloper etymology, interloper origin, 英语词源]