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?
2Before we start seeing NGrams and Google hit counts, let me point out in advance that there is a malady known as third nerve palsy, which will nullify any of those search strategies.– RobustoJun 17, 2011 at 1:41
@Robusto I didn't know that, but it could be why my friend used the term if she was familiar with the malady.– Spare OomJun 17, 2011 at 2:00
@Robusto - I had never heard of that malady (or, rather, I've certainly seen it but never knew its name.) I'd also never heard the phrase "you're getting on my third nerve," but I believe I might start using it - the image of going literally cross-eyed with frustration is irresistible. (My apologies to any actual sufferers of the malady, as no offense is intended.)– MT_HeadJun 17, 2011 at 3:50
1@Robusto, actually you are not right - ngrams.googlelabs.com/… , but only because third nerve yields no hits (in this form) ;)– UnreasonJun 17, 2011 at 9:50
@MT_Head, I believe my friend made up getting on my third nerve. I'm sure she wouldn't mind you putting the phrase into circulation. :)– Spare OomJun 18, 2011 at 19:23
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).
I can't accept a comment as the answer, so linking the comments in your answer works. Jun 18, 2011 at 19:28
The "third track" refers to the live electric track on the subway tracks. As in "don't touch the third track". I think that is another connection to referring to the "third nerve" - it's the one that has an unwelcome consequence.