# Why are cup sizes referred to as “double X” not “X squared” or “two X's”?

When it comes to bra sizes, there are many different design standards and sizing systems. In Continental Europe there's an often used scale that is simply a letter between [A - Z], where each letter represents a 2cm difference between underbust and bust circumference.
But for example in the UK, the scale might go something like this:
[AA, A, B, C, D, DD, E, F, FF, G, ... ] (note the double-letters), where each step of the scale is a 1 inch difference in bust size.

There are many variations to these systems, but mosten often they include sizes that are represented by double letters, e.g. "AA", "DD", etc.
NOTE: Exceptions to this would be the aforementioned system that is in use in Continental Europe, and a system that is sometimes (rarely) used in the US, where these double-letter sizes are instead denoted as XN, where X is a letter between A-Z, and N is a number between 1 - 9, e.g. DD = D2.

Now I was wondering, in mathematical contexts you'd pronounce "DD" as "D times D", or "D squared". Would there be an etymological reason as to why cup sizes are pronounced in a way that clearly goes against this well established mathematical standard?

Shouldn't "Double D" refer to "D2", and "D squared" to "DD"?

• What makes you think that mathematics should have anything to do with it? – Hot Licks Dec 3 '17 at 4:06
• @HotLicks I don't know. I thought it might. – user7003859 Dec 3 '17 at 4:11
• Would you say that brassiere is spelled with a double s? It's not unusual to use double like this, as has been done for many centuries before the invention of bras (checking OED at least since 1599). – Laurel Dec 3 '17 at 4:16
• @Laurel Ah, I see. I'm not a native English speaker, so I usually think of two consecutive s's as "two s's", not "double s", in my mind. But now that you mentioned it, I do realize that "double X" is a common way to refer to two letters. My mistake. If you want to submit an answer referring to your comment, I'll accept it. – user7003859 Dec 3 '17 at 4:21

According to Wikipedia, bras were first measured with letters in 1932; this system used just four letters: A, B, C, and D. I'm not sure when the "double D" measurement was first used, but it was surely after that.

However, calling two consecutive identical letters "double" (e.g. "double e") is much, much older, well predating the modern bra. OED has several citations that show this:

The Italian when he vttereth any Latin word wherein this letter i is to be pronounced long, doth alwaies pronounce it as a double e, viz. as ee.
Coryats crudities (1611)

This one is OED's earliest citation for "double u", although I'm not sure why it was written with a "w":

The latyne, Italiane, frenche, and spanyshe haue no doble W.