TLPI is a fantastic reference book to have when written code.
$ info Groff | awk '$2 == "History"{f = 4};f && f--' RS= ORS='\n\n'
1.2 History
===========
'troff' can trace its origins back to a formatting program called
'RUNOFF', written by Jerry Saltzer, which ran on the CTSS (_Compatible
Time Sharing System_, a project of MIT, the Massachusetts Institute of
Technology) in the mid-sixties.(1) (*note History-Footnote-1::) The
name came from the use of the phrase "run off a document", meaning to
print it out. Bob Morris ported it to the 635 architecture and called
the program 'roff' (an abbreviation of 'runoff'). It was rewritten as
'rf' for the PDP-7 (before having UNIX), and at the same time (1969),
Doug McIllroy rewrote an extended and simplified version of 'roff' in
the BCPL programming language.
In 1971, the UNIX developers wanted to get a PDP-11, and to justify
the cost, proposed the development of a document formatting system for
the AT&T patents division. This first formatting program was a
reimplementation of McIllroy's 'roff', written by J. F. Ossanna.