In my research a few weeks back, I went down the rabbit hole of region based memory management, and Cyclone was one of the first languages I came across (the majority of academic papers on the topic retrofitted an existing language- usually C).

I might be wrong here, so please feel free to correct me if so, but I don't think borrowing was a concept, per se, of the language itself.

As you mention, the concept the Rust designers took from Cyclone was explicit lifetimes.

Borrow checking provides two features (but in my opinion in a very un-ergonomic way): (1) prevention of use after free; and (2) temporal memory safety (i.e. guaranteeing no data races, but not eliminating race conditions in general).

I'm still wobbly on PLT legs though; I'm sure there's a pro or ten who could step in and elaborate.