Haskell also has only one namespace. I propose that Clojure took it from there, including persistent data structures, lazy data structures, ...
> But loop/recur sure looks to be ultimately inspired by Scheme style use of TCO;
To me it looks more like ancient Lisp with prog and goto.
(defun foo ()
(prog ((a 1))
start
(print a)
(when (< a 10)
(incf a)
(go start))))
loop/recur is of course much less powerful than TCO, because the JVM doesn't natively support it (it's not trivial, security wise). There are three other Lisps on the JVM that I know of: SISC Scheme is mostly dead but does TCO at a cost in speed, Kawa Scheme has as of late added fine grain control over TCO, and Armed Bear Common Lisp doesn't try, as Common Lisps are not required to.
But loop/recur sure looks to be ultimately inspired by Scheme style use of TCO; I just did a set of functions using it for the first time and everything I learned from SICP/6.001 applied and made that part of it trivial.