Since the earliest versions of Emacs developed at ProjectMac, an online help system was incorporated as early as the TECO implementation of Emacs. This hypertext “Info system” was available and ported alongside with Emacs to the [[TENEX?]] and [[TOPS-20?]] environments. Info files also freely distributed with the system covered everything from “Cambridge restaurants” and “the system calls for the TOPS-20 operating system itself”.
In the 1970’s at Carnegie Mellon University (CMU), Brian Reid developed a program and format named [[Scribe?]] to mark up documents for printing. It used the ‘@’ character to introduce commands, as Texinfo does. Much more consequentially, it strived to describe document contents rather than formatting, an idea wholeheartedly adopted by Texinfo.
Meanwhile, people at MIT developed another, not too dissimilar format called [[Bolio?]]. This then was converted to using TeX as its typesetting language: BoTeX?. The earliest BoTeX? version seems to have been 0.02 on October 31, 1984.
BoTeX? could only be used as a markup language for documents to be printed, not for online documents. RichardStallman worked on both Bolio and BoTeX?. He also developed a nifty on-line help format called Info, and then combined BoTeX? and Info to create Texinfo, a mark up language for text that is intended to be read both online and as printed hard copy.
As the development of GnuEmacs and creation of EmacsLisp began, RichardStallman used the above ideas to synthesize a single documentation source format that could be portable for being printed and be available as HyperText? within Emacs.