I've had someone tell me that C++98 was written under ANSI before being formally standardised as ISO/IEC 14882:1998.
I know that ANSI was involved with C, but I can't seem to find much in the way of proof that the phrase "ANSI C++" is terribly accurate.
Initially, in '89, the standardization of C++ was handled by ANSI X3J16. Starting in '91 ISO WG21 joined in. You may want to read BS's A History of C++:1979-1991. IMO, "ANSI C++" is just a leftover name; the language is "ISO C++" even though ANSI is indirectly involved in the standardization.