word-forming element meaning "in; into," from French and Old French en-, from Latin in- "in, into" (from PIE root *en "in"). Typically assimilated before -p-, -b-, -m-, -l-, and -r-. Latin in- became en- in French, Spanish, Portuguese, but remained in- in Italian.
Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" (encircle), also "cause to be, make into" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as ensure/insure, and most en- words in English had at one time or another a variant in in-, and vice versa.
"catalogue consisting of names in a row or series," c. 1600, from Middle English liste "border, edging, stripe" (late 13c.), from Old French liste "border, band, row, group," also "strip of paper," or from Old Italian lista "border, strip of paper, list," both from Germanic sources (compare Old High German lista "strip, border, list," Old Norse lista "border, selvage," Old English liste "border of cloth, fringe"), from Proto-Germanic *liston, from PIE *leizd- "border, band."
The original Middle English sense is now obsolete. The sense of "enumeration" is from strips of paper used as a sort of catalogue. The native Old English form of the word lingered as list in a few specialized senses. List price is from 1871.