interloper n.

word-forming element used freely in English, "between, among, during," from Latin inter (prep., adv.) "among, between, betwixt, in the midst of" (also used extensively as a prefix), from PIE *enter "between, among" (source also of Sanskrit antar, Old Persian antar "among, between," Greek entera (plural) "intestines," Old Irish eter, Old Welsh ithr "among, between," Gothic undar, Old English under "under"), a comparative of root *en "in."

A living prefix in English from 15c. and used with Germanic as well as Latinate words. Spelled entre- in French; most words borrowed into English in that form were re-spelled 16c. to conform with Latin except entertain, enterprise. In Latin, spelling shifted to intel- before -l-, hence intelligence, etc.

c. 1200, from Old English hleapan "to jump, spring clear of the ground by force of an initial bound; run, go; dance, leap upon (a horse)" (class VII strong verb; past tense hleop, past participle hleapen), from Proto-Germanic *hlaupanan (source also of Old Saxon hlopan, Old Norse hlaupa, Old Frisian hlapa, Dutch lopen, Old High German hlouffan, German laufen "to run," Gothic us-hlaupan "to jump up"), of uncertain origin, with no known cognates beyond Germanic; perhaps a substratum word.

First loke and aftirward lepe [proverb recorded from mid-15c.]

Transitive sense "pass over by leaping" is from early 15c. Leap-frog, the children's game, is attested by that name from 1590s ("Henry V"); figurative use by 1704; as a verb from 1872. To leap tall buildings in a single bound (1940s) is from the description of Superman's powers. Related: Leaped; leaping.

"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.