It's because there are a ton of Ruby implementations. MRI is the name for the official one that Matz works on.
If he said "Ruby's method caches," he would be wrong, this is about details of MRI specifically, and not, say, JRuby or Rubinius.
Given how much hackers love TLAs, and that there are what, 2600 of them, it's inevitable that there will be some amount of namespace clash. Ruby people reading a Ruby blog post aren't going to be confused about it, and while others may have momentary confusion, a few seconds later it's pretty clear what's being discussed.
Yeah, and while we're at it god forbid someone name a language after a colloquialism for a popular brewed and caffeinated drink. Or the island the beans for said drink sometimes come from. Or a snake that sometimes lives on that island...
If I told my parents I worked in Ruby all day they'd think I started a career in precious gem mining, who cares? "Those who know what it is will know..." are exactly 100% of the people that care about Matz's Ruby Interpreter and therefore this article.
Ruby isn't an acronym. Neither is Java. JVM is though, and the entire first page on google for JVM is about the java virtual machine. Had they called it MRI for java viRtual MachIne, it would still not be all over the front page.
There are 17,576 possible 3 letter acronyms. I would argue that its awefully hard to find one that isn't overloaded. Worse even when your acronym is comunityn generated. "Matz' Ruby Interpreter" likely wasn't named by matz himself.
> ... At this point, it started seeming somewhat impractical to go and patch rails and all these other gems that I use, so I decided to investigate the amount of effort that would be required to actually solve the problem in MRI. ...
I admire James. Wading into the interpreter takes balls.