Okay, call this a two stage answer with both parts from the etymology website I really like.
Though I would most likely have never guessed the word’s existence, once seeing it, my idea of what its components were was correct but I didn’t have any idea what language they had originated in.

Part 1:
https://www.etymonline.com/word/en-?ref=etymonline_crossreference#etymonline_v_8621
“en- (1)
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.

en- (2)
word-forming element meaning “near, at, in, on, within,” from Greek en “in,” cognate with Latin in (from PIE root *en “in”), and thus with en- (1). Typically assimilated to em- before -p-, -b-, -m-, -l-, and -r-.”

Part 2:
https://www.etymonline.com/word/ensorcell
“ensorcell (v.)
also ensorcel, “to bewitch,” 1540s, from French ensorceller, from Old French ensorceler, a dissimilation of ensorcerer from en- (see en- (1)) + verb from sorcier “sorcerer, wizard” (see sorcery). Related: Ensorcelled; ensorceled.”

(Next question, what does “dissimilation” mean? Now I gotta go look that up.)

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