Thanks for the info. I did not know this, but it does not surprise me. I am sure there are similar examples.

The first section of the linked article says that Fortran "was an odd choice from a pure computer science standpoint", that they "developed hardware optimized to run FORTRAN", and that large parts of the OS (in particular, the kernel) were eventually rewritten in other languages.

This is, in my opinion, a great example of how Fortran could not compete with C as a systems programming language.