Source : Webster's Revised Unabridged Dictionary (1913)

Noddle \Nod"dle\, n. [OE. nodil, nodle; perh. fr. nod, because
   the head is the nodding part of the body, or perh. akin to E.
   knot; cf. Prov. E. nod the nape of the neck.]
   1. The head; -- used jocosely or contemptuously.

Source : WordNet®

noddle
     n : an informal British expression for head or mind; "use your
         noddle"