Nott: Hnott, Saxon, smooth, round, a nut. Notted, an old word for shorn, polled. The name may have come from wearing the hair short and smooth. "A nott hed had he, with a brown visage."--Chaucer.
Moody: descriptive, from disposition (from the Welsh), a hermit or monk
http://www.last-names.net/

From Ancestry.com:
Crabb - Middle English, crabbe, a crustacean, descriptive for his walk; a crabapple tree; or German/Dutch, Krabbe, someone who sells seafish or catches it
http://www.ancestry.com/search/SurnamePage.aspx?html=b&ln=Crabb&sourcecode=13304
Goyle: No info about surname
McNair: Gaelic Mac Iain Uidhir ‘son of sallow John’; Gaelic Mac an Oighre ‘son of the heir’; Gaelic Mac an Mhaoir ‘son of the steward or keeper’
http://www.ancestry.com/search/SurnamePage.aspx?sourcecode=13304&html=b&fn=&ln=mcnair&submit.x=0&submit.y=0
Riddle: habitational name from Ryedale in North Yorkshire
http://www.ancestry.com/search/SurnamePage.aspx?sourcecode=13304&html=b&fn=&ln=riddle&submit.x=0&submit.y=0
Lupin: No info about surname (I think this one was a lead-in to the fact that he's a werewolf - Lupus = wolf)
Vance: Old English fenn
Avery: Anglo-Norman French personal name Auvery, a Norman form of Alfred; Anglo-Norman French personal name Aubri
http://www.ancestry.com/search/SurnamePage.aspx?sourcecode=13304&html=b&fn=&ln=avery&submit.x=0&submit.y=0
Pettigrew: Scottish (of Norman origin): probably a nickname for a small man, from Old French petit ‘little’, ‘small’ + cru ‘growth’; Another possible explanation is that it is a nickname for a man with long thin legs, from Old French pie de grue ‘crane’s foot’
Black: http://www.ancestry.com/search/SurnamePage.aspx?sourcecode=13304&html=b&fn=&ln=black&submit.x=0&submit.y=0
Snape: Old English snæp ‘area of boggy land’. In Sussex the dialect term snape is still used of boggy, uncultivable land.
http://www.ancestry.com/search/SurnamePage.aspx?sourcecode=13304&html=b&fn=&ln=snape&submit.x=0&submit.y=0

I think most of the Purebloods will have the Norman association (excepting 'Potter', which is obviously a tradesname). The WW probably followed along the same lines as their Muggle neighbors. Maybe the French/Norman wizards came over around the same time as Wm the C?