The first ‘nervous’ points to the nervous system.
The second ‘nervous’ points to the emotional response.
A ‘nervous reaction’ presumably can mean an emotional response OR a chemical reaction in the central/peripheral nervous system, though I think that would be called ‘neurochemical reaction’.
That’s not my question.
My question is, is there a reason why those terms are homonyms? They are somewhat related to each other. I am told/have heard before that the prefrontal cortex plays a roll in reason and emotion, as if reason and emotion are actually interrelated. There are also common English phrases, like the following:
“I don’t have the nerve to…”
“I shan’t lose my nerve to…”
I pose a hypothesis. I think, back in the olden days, people used ‘nervous’ to mean the emotion, because it was one that manifested on the face. Later, as people found out about how the brain played a roll on emotion, including the nervous emotion, they named the nervous system ‘the nervous system’. As for the two English phrases, I think, back in the olden days, people believed that having the ‘nerve’ meant someone who was courageous or brave or valorous or having the lack of nervousness. On the other hand, I may be totally wrong altogether, because I clearly have made up the hypothesis without any real source or citation.
You could always look for an authoritative citation from the dictionary. Here are the entries for “nervous” and for “nerve.” The origin of both words appears to be the latin “nervus,” which originally referred to sinew or tendon.
That’s a start, anyway. In reference to the nervous system, it apparently speaks to the fibers/wires that make up the nervous system. In reference to the emotional state of being nervous, it may refer to the physical tension in all the sinew and tendons of the body. In reference to courage, to have “nerve” may mean to have the requisite fiber (moral, muscular, or both) to do daring deeds.
It means they have a poor understanding of the common usage of the word “nerve” and opt to use “nerves” instead. A bit like “honing in” on something instead of “homing in,” or “pouring over” something instead of “poring over” something."
She makes ya tense up all your sinews and tendons.
To make things more complicated, in Britain "nervy means nervous (in the emotional sense), or inclined to nervousness, whereas in the USA “nervy” means something like bold or courageous.
Knowledge of the human nervous system, its connection to the brain, and that nerves are different from sinews, goes back to the work of Herophilos and Erasistratus in the 4th-3rd centuries BC. The understanding that the nervous system, including the brain, is largely responsible for emotional states is a lot older than the English language.
