TL; DR: "mock" and "stub" were the common terminology when RSpec's
API was first created but we've realized that using them
to create fake objects causes confusion and that
a much better term.
I wasn't around when RSpec's original APIs were created, so this is a bit of guess work, but here's my understanding.
When RSpec's mocking API was first created, the two common terms used for what we now commonly call "test doubles" were mocks and