Decades ago, lots of programming languages were created that hardly anybody knows now, including some that would definitely be considered very specific, researc

Decades ago, lots of programming languages were created that hardly anybody knows now, including some that would definitely be considered very specific, research-oriented, etc. This isn't really a new thing. See for example Jean Sammet's _Programming Languages: History and Fundamentals_. Edit: Bergin & Gibson's _History of Programming Languages, Volume 2_ is pretty good, too, but that one covers more recent languages: Prolog, C, Forth, Lisp, Icon, etc. It's not a bad idea to read about old experimental designs, particularly those that didn't work out because of limited hardware. I think there's a lot of potential in the APL and concurrent / constraint logic programming families.