In roguelikes, items made by the elves have a reputation of high quality. These are usually called elven items, but “elvish” was chosen because it ends with “sh”, a long tradition of Unix shells. It also rhymes with fish, one of the shells that influenced the philosophy of Elvish.
The word “Elvish” should be capitalized like a proper noun. However, when referring to the
elvish command, use it in lower case with fixed-width font (like in this sentence).
The adjective for Elvish (as in “Pythonic” for Python, “Rubyesque” for Ruby) is Elven.
Whoever practices the Elvish way is called an Elf. The GitHub organization is called Elves for this reason.