All three of the following surnames were originally derived from placenames, although the exact location of that name is open to a little doubt.
Nancollas is a surname which has a long association with St Austell. John Nancolas was found in that parish in 1543. But there is nowhere called Nancollas in Cornwall. One possible origin is Nanscoras, meaning valley of the fish-pond or weir. There were two places with this name in medieval Cornwall, one at Constantine and the other at St Just in Roseland. The original Nancollas might have hailed from one of those more westerly places, their name undergoing change in the move east. Another possibility is Nancolleth (valley of the hazel trees?) at Newlyn East. This was pronounced Nancolla by the 1570s and had given rise to a surname Nancolla. The problem is that Nancollas at St Austell predates Nancolla at Newlyn East. Or was there a lost placename nearer St Austell?
Nanscawen, meaning valley of the elder trees, looks clearer. There was just one place spelt Nanscawen in the late medieval period – at Luxulyan – although we also find a Nanscaw at St Breock. Either could have given rise to the surname Nanscaven found at St Columb Major in the early 1500s. Yet by the mid-1600s this surname was only found many miles away, to the east of Bodmin Moor. By the 1700s it had drifted southwards, where it remained in south east Cornwall around Saltash. Does the historical geography of this family name betray its migration from mid-Cornwall? Or was there a connection with the suspiciously proximate Liscawn at Sheviock? This was spelt Lescawn by 1433 but was originally Nanscawen.
Netting is also from a placename. The surname first appeared as Netton, Nettin or Netting in south east Cornwall during the 1600s, although there was an isolated Netyn occurrence at St Austell in 1592. It remained confined mainly to the south east into the 1800s, with one or two further examples art St Minver on the Camel estuary. It’s most likely to have evolved from the surname Newton. There are 25 places called Newton in Cornwall, 17 with examples of spellings earlier than 1600. Any one of these could have given rise to the surname. Not surprisingly this English placename was found mainly in east Cornwall, where Netting also emerged.