I worked at one place, they had heavily invested into pick style databases, when pick databases still made sense, and for some of the crusty old pick programmers still around, that was the os, it was their development environment and shell.

https://en.wikipedia.org/wiki/Pick_operating_system

Note: I don't think they had any actual pick systems left, by the time I got there they were mostly using unidata on linux, but there were still a lot unidata on sco boxes around.