Scheme
Scheme is a general-purpose, functional programming language that emphasizes simplicity and minimalism. It is often used for teaching computer science concepts, as well as for research and scripting tasks.
Hello, world code example:
"Hello world!"
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 18,011