I know that many Eiffel libraries are quite well known, mostly the ones shipped with Eiffel Studio, which also includes Gobo Eiffel libraries.
However, even among those libraries, there are a few that are barely known by the users.
Designing a programming language is an difficult task. During my time in academia, I had the great pleasure to meet some language designers. Listening to their stories is highly educating. Things that look simple or arbitrary at first become deep insights into the way humans understand problems and model solutions. There is nothing trivial in deciding names of keywords or punctuation.