What do you say, and what do you hear others saying? "Argon-mercury" or "Mercury-argon"? How long have you been using the term you use? I'm curious to see which one is more common. Thanks! 

I, too, have often wondered if this was a regional difference or perhaps just a matter of habit and initial learning.  I have, for decades, used the terminology of "Mercury-Argon"  or sometimes even just "mercury" for shorthand if I knew that my audience understood.  

This was most likely born out of how I first heard it referred to, however, it made sense as the Mercury becomes the dominant spectral trait in such a tube and the Argon is mostly just used as the carrier gas to get the ionization going and only contributes a small percentage to the overall UV output to excite the phosphors. 

However, while the same would be true if Neon or another rare gas was used with Mercury, I instead refer to those as "Neon with Mercury" or "Krypton with Mercury" etc.  I did, at one time, ask myself why exactly I would be inconsistent in this regard and I came to the conclusion that my reasoning for the latter examples is simply because it is not a standard and commonly used combination.  Most neon filled units do not have mercury added to them unless you specifically want the color shifting effect from it.  FWIW-- I actually do exactly this in many of my art pieces as I do like the effect, but beyond that, it is not a common practice.  (do note that in cold climates, a mixture with a high percentage of Ne vs Ar is used as the neon will run hotter and help vaporize mercury for better output in phosphor coated tubes when outdoors in winter.....a 75/25 Ne/Ar mixture plus Hg being a common example, although I have seen straight neon used for this purpose too)

So, while that incsonsistency of nomenclature would normally be something that bothers me, I have, over the years, managed to forgive myself for it due to the above line of reasoning even if some may find it flawed.  

I believe it to be "Argon with Mercury!" or "Ar with Hg."

We usually refer to them as mercury tubes unless they don't have Ar as the carrier gas then it's "neon with mercury" or whatever gas you're using. 

If ever I am describing a typical argon with mercury tube I say "argon with mercury" maybe because that's the order we put them in the tubes? 

I imagine it's a regional thing or just how you're taught- like seals/welds/joins or pumping/processing/bombarding.

Thank you all three for your thoughtful input. I agree that it's probably all of those things: generational (depending on when you got into it), regional, and cohort-based (who you learn from and hang with). Great example of seals/welds/joins! I'll pass this on to the people who were asking me. 

Regarding the seals/welds/joins  --  In neon parlance, we "seal-off" or "tip-off" a tubing unit from the manifold.....Using a tool often called a "tipping torch".....which should imply that we sealed the two bits of tubulation glass to attach it.  However, very often, the joining of two sections of tubing---be it tubulation or otherwise, gets referred to as welding.  However, if you are working with those who are scientific glassblowers, "sealing" is correct in that situation and for them, "welding" is more akin to what is done in the metal shop but with glass-- two pieces are put together using heat and another piece of glass as a filler material--just like welding steel and feeding a welding rod.  Since I tend to swim in both pools, I find myself jumping around with terminology depending upon who I am speaking with and what the details are.

Add to this the various names for different torches over the decades and regions and you can readily confuse or unconfuse someone.  (I once wrote an article about the torch names....maybe an article on other terminology is in order, too.)

Dydia,
I was looking through some other old stuff today and may have found a more definitive answer to the original question:   Most of the older books and documentation, such as transformer footage charts from the pre-WWII era, simply specify "Mercury" or "Mercury-Argon" for such tubing.  So there you have it.   If you require imagery of these old charts or book pages, let me know and I will get them to you.