Ruby didn't always had both. `reduce` as an alias for `inject` was introduced in Ruby 1.8.7; `filter` as late as in Ruby 2.6 (just a few years ago, and most of the codebases I saw are still preferring `select`).

Yes, the dictionary is normalized in the last years towards what became industry/mainstream standard names for the concepts, but the statement that initial names were derived from Smalltalk is correct.