I haven't written any ruby for over a decade and a half, when ruby 2.x was still on the horizon. But I do know the source of "eigenclass". It was first jokingly used in an odd instructional programming book / web comic / experimental art piece by "why the lucky stiff" who was briefly prominent in ruby-land then erased himself from the internet. It's funny that it has now become an established term of art for Ruby people.
splat is the official name in Ruby, spread comes from the similar JS construct (obviously, lots of people using Ruby also use JS, so its natural for terminology from one context to sometimes get applied to similar concepts in the other even where it isn’t official.)
I read it after college when I first started working with Rails 1 after I joined a friend’s company. Funny to think that was almost two decades ago. I still remember the quirky art style, although I will admit to preferring a more prosaic book when I learned the language. But it was a fun community and the sense of creativity was really apparent.
