A transitional name for the C with Classes language before it was known as C++. The name was eventually abandoned because it was considered ugly and crude, and because it was predicted the next standardization of C would occur in 1985. Because it was somewhat traditional to name a standard language the name of the language plus the year of standardization, this would mean C would become C85. As C84 was supposed to be a superset of C, it would have been embaressing for it to have an earlier year in its name.

I think we're all glad they chose C++ in the end.