Receiving fellatio from a resident of an extremely rural area, such as a redneck. The giver of the fellatio may or may not be of distant relation to the receiver.
I met my second cousin out in the corn field and got some of that neck neck.
A command to tell someone to go away or leave them alone. The words themselves (neck and necker) are probably meaningless, though could be related to the older English phrase you've got some neck. Similar to buzz off, piss off, take a hike.