Unix history is detailed in various books, like Peter Salus’ “A Quarter Century of Unix,” with some inaccuracies. Bell Telephone Laboratories (BTL) collaborated with MIT and GE in the Multics project, where Ken Thompson and Dennis Ritchie worked. BTL eventually withdrew from Multics in 1969 due to slow progress, making way for Unix’s creation. Unix, initially a joke name referencing Multics, excelled due to its simplicity and efficiency. Unix borrowed technical ideas from Multics, like error recovery and command parsing. Despite popular belief, Multics didn’t fail but achieved most of its goals before Unix’s emergence. The evolution and impact of Unix are profound and have left a lasting legacy in computing.
https://www.multicians.org/unix.html