It's not as much a mystery as you think, the Kernel module is pretty well documented and states right in the first paragraph that its methods are available in a

It's not as much a mystery as you think, the Kernel module is pretty well documented and states right in the first paragraph that its methods are available in all Ruby objects: https://ruby-doc.org/core-3.0.2/Kernel.html https://ruby-doc.org/core-3.0.2/Kernel.html