Out of curiosity I looked up the history of isize and usize in Rust, which correspond to size_t in C++.
It turns out these types were originally named int and uint. The core team initially decided that int was a reasonable name, but then changed their minds after community feedback and after discovering incorrect uses of int in the stdlib, libraries, and even the Rust docs. The name was changed to isize to more clearly signpost the type’s purpose.
Folks here may find those old Rust threads insightful.