*Getting on one's nerves*, *last nerve* or *third nerve*?

I'm quite familiar with the idiomatic phrase of getting on one's nerves, but less so with getting on one's last nerve, though I had a friend who used a variation: getting on one's third nerve. Is one version preferred over the other in different locations? Is third nerve used anywhere?

Solution 1:

It is a small difference in meaning, as "last nerve" is a bit stronger than just "nerves".

Getting on one's nerves

Indicates that the person is strongly annoyed by someone/something.

Getting on one's last nerve

Indicates that the person has been so annoyed (maybe over a period of time) that he is on the edge to snap.

Getting on one's third nerve

This is one I have not heard before, but I think this is well answered in the comments already posted to the question (initiated by @Robusto with his reference to third nerve palsy).