And suddenly a german word :O

"verboten" is german for "forbidden"

src/doc/book/variable-bindings.md

@@ -102,7 +102,7 @@ mutation, then the solution is quite easy: add `mut`.
 There are other good reasons to avoid mutable state when possible, but they’re
 out of the scope of this guide. In general, you can often avoid explicit
 mutation, and so it is preferable in Rust. That said, sometimes, mutation is
-what you need, so it’s not verboten.
+what you need, so it’s not forbidden.
 
 # Initializing bindings