Objective-C++ was introduced in the early aughts (https://luminaryapps.com/blog/objective-c-a-history/index.ht... says 2002; I remember watching the WWDC video in which it was introduced but I'm having trouble finding it now, sorry).

You're talking to someone that has hold NeXT manuals for an university porting project, and in fact the very first editions of Apple documentation have exactly the very same manual, rebranded for Apple.

And just not to be a random dude in the Internet, here are the NeXT documents straight out of 1993, page 173.

http://www.bitsavers.org/pdf/next/Release_3_Nov93/Object-Ori...

Page 31 on "Developing business applications with OpenStep"

https://archive.org/details/developingbusine00gerv/page/n7/m...

Finally, from the language authors themselves, chapter 15, Objective-C++ (1989-1990)

"The Origins of Objective-C at PPI/Stepstone and Its Evolution at NeXT"

https://dl.acm.org/doi/pdf/10.1145/3386332