nerve

a bag of nerves: seebag.

get on someone's nerves irritate or annoy someone. informal

have nerves of steel not be easily upset or frightened.

live on your nerves (or your nerve ends) be extremely anxious or tense.

strain every nerve make every possible effort.

☞ Nerve is used here in an earlier sense of 'tendon or sinew'.

touch (or hit) a (raw) nerve provoke a reaction by referring to a sensitive topic.

a war of nerves: seewar.