Etymology
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interloper (n.)

1590s, enterloper, "unauthorized trader trespassing on privileges of chartered companies," probably a hybrid from inter- "between" + -loper (from landloper "vagabond, adventurer," also, according to Johnson, "a term of reproach used by seamen of those who pass their lives on shore"); perhaps from a dialectal form of leap, or from Middle Dutch loper "runner, rover," from lopen "to run," from Proto-Germanic *hlaupanan "to leap" (see leap (v.)).

OED says Dutch enterlooper "a coasting vessel; a smuggler" is later than the English word and said by Dutch sources to be from English. General sense of "self-interested intruder" is from 1630s.

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interlope (v.)
"intrude where one has no business," especially with a view to gain the advantage or profits of another (as a trader without a proper licence), early 17c., probably a back-formation from interloper (q.v.). Related: Interloped; interloping.
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