EDLIN (short for "editor of lines") was actually originally written for and included with
Seattle Computer Products'
QDOS. It was written by QDOS' author and grand pappy of MS-DOS
Tim Patterson. Patterson didn't want his operating system to ship without an editor, so he hacked it together in a week. Patterson did not want to put a lot of work into an editor since QDOS (and EDLIN) would only be need for about six months when
Digital Research released its long promised
8086 version of
CP/M.
EDLIN was included in all versions of MS-DOS up to and including
DOS 5.0. It was put to rest after that.
EDIT became Microsoft's errr improved DOS text editor for DOS 5.0 and onward.
EDLIN has long spawned a lot of jokes, including some often reproduced spoof documentation for a supposed Microsoft product called "
EDLIN for Windows".
Google for it if you like.