LAP wrote
"Not something of direct relation to mining... but it's interesting to see how names develop. anyone idea where the name "Dinorwig" came from. Presumably once to seperate words."
Dinorwig was originally two words the Din part in this case means fort (shortened form of Dinas which in modern term usage can mean city ie Dinas Bangor). The fun starts when starting on the second part, 'orwig'. Some have put forward the idea that it comes from Norwig, that is Norwegian. However the emminent Welsh scholar Sir John Rhys, was of the opinion that the Orwig was a modern variant of Ordivice, the celtic people of Mid to North West Wales. This is where we get a bit off topic. Towards Y Felinheli (Portdinorwig) is Dinas Dinorwig an iron age hill fort SH550653 (the extra dinas is a tautology). This is a form of bi-vallate construction, different from most hill forts in the area except Dinas Dinlle. (If you stand on one you can see the other). Sir John Rhys had the theory that these were ordivician and imposed on an earlier grouping hence the naming by a local population, because if the area was always ordivian why name one fort in particular.
Now how it came to be given to a nearby village I've no idea. However, a few villages in the area have renamed in recent times, for example Rachub was originally Cae Llwyn Grydd (Rachub being just one street originally).