Nan Curunír (i.e. the "Valley of Saruman") was the name given to the southernmost valley of the Misty Mountains, at the foot of the mountain Methedras.
Nan Curunír was named in the Third Age and soon became the location of Isengard.
The name 'Curunír' comes from the original name of the white wizard Saruman
who settled there, so therefore 'Nan Curunír' meant 'Saruman's Vale' in Sindarin