[schindlabua]

It would have been bootstrapped in assembly (or B/BCPL?) and then once you can compile enough C to write a C compiler you rewrite your compiler in C.

I remember a Computerphile video where prof. Brailsford said something along the lines of "nobody knew who wrote the first C compiler, everybody just kinda had it and passed it around the office" which I think is funny. There's some sort of analogy to life and things emerging from the primordial soup there, if you squint hard enough.