A decade before yacc was even an idea, or the events that eventually made UNIX.
A fine example of systems programming, e.g. compiler writing, in high level languages, before the myth of C making it all possible.
I wasn't disparaging Meta II; just noting that it was evidently the first precursor of something we all take for granted. And also, I'd just happened to hear the old rock'n'roll song Yakety-Yak.