node; plural noun: nodes

a point at which the amplitude of vibration in a standing wave system is zero.

a point at which a harmonic function has the value zero, especially a point of zero electron density in an orbital.

a point of zero current or voltage.

late Middle English (denoting a knotty swelling or a protuberance): from Latin nodus ‘knot’.

nod (third-person singular simple present nods, present participle nodding, simple past and past participle nodded)

(transitive, intransitive) To incline the head up and down, as to indicate agreement.

and to add... the "nods" is also a term used amongst those who abuse opiates. When they get dangerously high, youd see their head start popping up and down as they try to stay awake...therefore theyre "on the nods."