 From Middle Irish , from Old Irish (from Anglo-Norman , from Latin ) + meaning castle (fortified building).The "waters" referring to the rivers Dinin (Dinan), Brokagh and Cloghogue meet, and the "castle" refers to the Norman motte and castle built in 1171 by William Marshal, 1st Earl of Pembroke.The plateau, with an area of , is in the southeastern of the Central Plain of Ireland.It is almost circular, except to the south-west where it is cut away to form the Dinin River Valley.