In reply to Anonymous:
Yes, but it's very early medieval latin (767), as OED says, 'of unknown origin', though many (including myself) believe it has Celtic roots.
This website:
http://www.etymonline.com/index.php?l=r&p=16
for example has:
'from M.L. rocca (767), from V.L. *rocca, of uncertain origin, sometimes said to be from Celtic (cf. Bret. roch ).'
It is interesting to note in passing that the legendary bird, the Roc, was also spelled 'roche or roque'.
'Roc' in ""modern "" Irish means wrinkle, ridge, furrow - perhaps originally it was applied to a landscape to imply a 'rough area' ... rocca, 'roughnesses'??
I believe it was probably very similar to many other very ancient Celtic/european words like Pic (peak), stac, cnoc (hill), and craig or carraig (crag - in celtic the g pronounced virtually as a c)