According to Helen who I work with, her daughter calls a bra a “booby vest”.
I think I have definitely got to start using that term myself. It tells you everything you need to know about the complex and mysterious items that are women’s underwear.
Viv tells me that the German for bra is “Bustenhalter”. This, again, is a very useful word to know. (My favourite German word is “Fussballrowdie” meaning ‘football hooligan’.)