(noun) “fibre conducting impulses to or from the brain”
The modern meaning was coming into the language in Shakespeare’s time, but from the beginning of the 16th century the word had a different anatomical sense: “sinew, ligament, muscle” still heard today in the idiom ‘strain every nerve’. A clue to the meaning can usually be found in the accompanying language. Thus Menenius talks of “the strongest nerves” (Coriolanus, I.i.136), Macbeth talks of his “firm nerves” (Macbeth, III.iv.101), and Hamlet refers to the Nemean lion’s nerve as “hardy” (Hamlet, I.iv.83). The metaphorical use of the word was also entering the language at the same time: “strength, vigour, forcefulness”, and this use is also to be found in Shakespeare. In The Two Noble Kinsmen (I.ii.69), Palamon talks of Creon “who only attributes The faculties of other instruments To his own nerves and act”. But the modern meaning is lurking in the wings, such as when Antony says to Cleopatra: “ha’ we A brain that nourishes our nerves” (Antony and Cleopatra, IV.viii.21).
David Crystal