Other forms: enclosed, enclosing, encloses
To enclose something is to shut it in on all sides — or to put it in with a letter. Two senses, one of them very formal.
The physical sense is about boundaries, so an enclosed garden has walls all round, and the historical enclosures fenced off common land in England and changed the countryside for ever. The letter sense is standard business English, and please find enclosed is one of the most familiar formulas in correspondence, now mostly replaced by attached in emails. The noun enclosure covers a fenced area and a document sent with a letter.
Enclose and include are one word arriving twice. Both go back to Latin inclūdō, in plus claudō, to shut; one came through French and kept the walls, the other came straight from Latin and kept the idea.
Proto-Indo-European
*(s)kleh₂w-
Middle English
enclosen
English, today
enclose
Built from
From Middle English enclosen, inclosen, from Middle English enclos, from Old French enclose, feminine plural past participle of enclore, from Vulgar Latin inclaudo, from Latin inclūdō (a doublet of include), from in- (“in”) + claudō (“to shut”), ultimately from Proto-Indo-European (s)kleh₂w- (“key, hook, nail”). Equivalent to en- + close.
Etymology from Wiktionary, CC BY-SA