OK, I got it. Since "the community" wouldn't spoon feed it to me, I actually did some looking up on my own. Here's my (very) quick and dirty explanation of why the "A" in A36.
To paraphrase what Steve Sells said earlier: there are component codes and construction terms....which still doesn't tell us what the "A" in A-36 stands for (A is for aardvark, etc).
So, here's what I found out after sorting out what Steve tried to tell me:
When it comes to steel (and other metalic products) there are generally two outfits that establish "standards": ASTM International and AISI.
AISI is the outfit that gives us one set of number/letter codes for steel products: "S" for shock resisting, "A" for air hardening, "10XX for carbon steels, etc.
ASTM gives us standards for all sorts of materials (rubber, plastic, iron and steel, copper, etc). It turns out that the section of their codes that deal with iron and steel products is the "A" section and all codes that fall under that section have an "A" prefix. A-36 is the spec for Carbon Structural Steel. Specs in the "B" section, for instance, apply to non-ferrous metals and alloys.
SO - the bottom line to all this is that the "A" in A-36 just stands for the section of the ASTM standards that deals with Carbon Structural Steel.
As Steve Sells alluded, we still can't mix apples and oranges when we talk about steel codes.