How to pronounce "nₒ" properly

People here (Hong Kong) like to pronounce n₀ ("n subscript zero") as "N-nor"; "N-zero" seems to be acceptable. I am wondering what's the most popular pronunciation in English.
I am actually a little confused by "N-nor". Where does it come from? Is it understood in America or England?

If you were reading it out to somebody, eg. to write down in a lecture, I would say N-sub-zero. But if this is a particular mathematical term then it's probably N-nought, or N-null. Sometimes the term has a particular usage from history or convention (eg the original paper or a famous textbook) whatever the rules of regular English grammar might say.

eg. the set of cardinal numbers is normally Aleph-nought or Aleph-null

From a native US English speaker:

As there don't seem to be any readily available pronunciation guidance resources on this subject, I am forced to be subjective. I believe "zero" is the most common, in the US, at least. Since I do not prefer to call "0" anything other than "zero" in any situation, I would say:

N-zero for nₒ

N-two for n₂

Etc.

As to your last question, I confess I wouldn't understand someone who said "N-nor", without further enlightenment.

Here in Canada we use 'N-nought'. I have NEVER heard N-zero or N-nor. This is solely from my experience, having taken many math courses in university.