One of my correspondents indicates that there was (is) a place named Nokere near Viane, south of Geraardsbergen.
The family name Van den Neucker is not uncommon in the region around Geraardsbergen - a short look at Geneanet suffices to see that. One tends to find the family name Neu(c)kermans slightly more to the north of Geraardsbergen, mostly around Ninove. But these are dangerous generalisations - the name Neuckermans was also known near Enghien.
In as far as I know there are two geographical centers for the Van den Neucker family name ; the region around Geraardsbergen, Enghien and Ninove ; and in and around Boom. Maybe, somewhere in a distant past, all the name bearers go back on a common ancestor, but the name derives from the walnut tree (oker) and that type of tree will not have been an uncommon presence in our past ... I would not dare to write that all the Van der Eycken, Van der Wilghen, Van der Linden a.s.o. go back on a common ancestor ...
It may not be totally useless to list some of the family names derived from the walnut tree.
My source is the "Woordenboek van de familienamen in België en Noord-Frankrijk" written by Dr Frans Debrabandere :
De Neucker, de Neuker, de Nucker, van de(n) Neucker, van den Euker, van de Neuken, Neu(c)kermans, Neukerman(s), Neu(c)kelmance, Nokerman(s), Nockerman, Nonckreman, Neukelmans, Neuquelman, Nuckelmans, Nuchelmans, Nuggelmans, Nochelmans, Ukelmans, Okerman(s), Ockerman, Ocreman, Ocqueman ...
Let it be known that I have nothing but disdain for the stupid morons who start grinning when I say I have Neukermanses in my family tree.
By the way, there also is a Nokere near Kruishoutem.