Bruce, I am afraid it is a spelling mistake, that Hadju is Hajdú. The other names in Hungarian spelling are:
Diósig in Hungarian is Diószeg, earlier they were three village: Bihardiószeg(it was the bigest), Érdiószeg, Diószeg. The Diosig is the Rumanian spelling of the Hungarian name, what means: Nut's corner.
You can see, where it was in Hungary, before the Trianon Treatment (near to the present Hungarian border in Rumania)http://lazarus.elte.hu/hun/maps/1910/bihar.jpg