It’s so bad that my fiancée has some bras that say she’s a B cup and others that says she’s a D cup. In order to go bra shopping, you have to actually try them on to find out if they fit.
If I had to try on underwear to see if they fit, I might not bother with underwear at all!
Probably around 14 or something. For whatever reason, people will often name DD as a large bra size around here. It also doesn’t exist in our bra size system. Some girl pointed out that non-sense at school.