Variants of the surname Nethery are Neathery, Netherly, Neatherly, and many others, It may have originated from a place called, "Netherby" in Northern England. According to http://genforum.genealogy.com/neathery/messages/1.html, The "Netherby"s of Northern England were banished to Ireland by James I, changing the name Netherby into Nethery.
This origin seems possible, but while doing my own findings, I may have a more plausible origin for the surname Nethery, which connects to the surname Nedry.
I think perhaps this surname Nedry is of Irish origin, and derives from the name Nuadha, the name of an ancient Celtic god. There are many surnames that derived from Nuadha, including the surname McNutt, which is from Gaelic Mac Nuadhat, the surnames Nutty, McNutty, Neddy, Nethey, Needy, and many others. I even found the surname McNedry, which supports this origin. http://www.ancestry.com/name-origin?surname=Mcnutt
The connection is that the surname McNutt is mostly found in Northern Ireland, and that the surname Nethery is mostly found in Northern Ireland also. Perhaps the surname Nethery is related to the surname McNutt, and that both surnames are of the same origin. If so, then this means the the origin of Nethery and Nedry are the same.
I came across a similar surname, Nedrow, an American surname only, and found out that some Nedrows have an Irish or Scottish origin. The surname Nedrow, according the the Dictionary of American Family Names, is of German origin, but perhaps there are a few Irish Nedrows out there too, having their origins from Naudha.
This message was edited by the author on September 7, 2012 at 4:24 PM