Old-school technical writing with groff
One of my favorite stories about Unix is how it turned into a text processing system. Brian Kernighan tells the story in his book Unix: A History and a Memoir (chapter 3) but to summarize: The Unix team at Bell Labs ran the original Unix on a PDP-7 computer, but it was a tiny system and didn't have sufficient resources to support new work. So Ken Thompson and others lobbied to purchase a new PDP-11 computer. Management denied the request. Around the same time, the Patents department planned to buy a new computer platform to produce patent applications using proprietary document formatting software. The Unix group proposed that the Patents department instead buy a new PDP-11 for the Unix team, and the Unix team would create formatting software for them.
That new formatting system was called nroff, short for "New Roff," an updated version of a text formatting program called Roff from a 1960s computer system. The name Roff came from the old expression, "I'll run off a document."