Yeah, I found "crust" to be rather counter-intuitive. I think one of the reasons that bugs me is that "ret" and "mut" don't have any intrinsic meaning in English, but my brain insists on reading "crust" as if it were a word.
"rustc" is how you invoke the compiler from the command line, that's no good. :)
I do seem to remember that the devs were passively soliciting ideas for a better name for this keyword. The great thing about a language at this stage is that if this really bothers you, then you can petition to have it changed!
I'd personally have gone with "rustc".