enamel v.

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.

"fuse or melt," especially ore, by heat, in a furnace, to separate the metal in it, late 14c. (implied in smelter "one who smelts ore"), from Dutch or Middle Low German smelten "to fuse, smelt, liquefy," from Proto-Germanic *smelt- (source also of Old High German smelzan, German schmelzen "to melt"), from PIE *smeld-, variant of PIE root *mel- (1) "soft." Thus the word is related to melt (v.). Italian smalto "enamel" is from dialectal smalzo "butter," which is from Germanic; compare enamel, email. Related: Smelted; smelting; smeltery.