Everyone knows how important documentation is -- for a project to grow past a certain point, it's a must-have. However, almost every software project of any size nowadays comes with at least a README file.
When did including a README file (specifically with that name) first become commonplace? It appears the first BSD kernel had a "READ_ME" file, so it must be pre-1977. But at least in the software packages listed here, it's not universal.