Ruby
Yukihiro "Matz" Matsumoto, 1995. Design principle: "optimized for programmer happiness". Dynamically typed, everything is an object, expressive syntax.
The story: Ruby on Rails (David Heinemeier Hansson, 2004) took it from a Japanese hobby to the world. Rails 1.0 (2005) defined the conventions-over-configuration paradigm for the web. YJIT (since Ruby 3.1) gives JIT compilation and 30–50 % speedup on Rails workloads.
Powers GitHub, Shopify, Stripe (partly), Airbnb (partly), Basecamp. "Mature" status — not growing but not shrinking. Renaissance in 2023+ with Rails 7 + Hotwire + Turbo showing that server-rendered + sprinkles of JS works well.