boob knickers

have you ever heard of boob knickers? no? neither had i...until earlier today.
see my younger brother is 3 years old, and i had a hoody on, and my brother was telling me to take it off, i was trying to avoid the embarrassment but my harrassing brother told me to get it off. so as i took off my jumper my top went with me, and my brother exclaimed "i can see your knickers" i bit confused by this comment as my trousers were still intact, he then exclaimed, i can see your boob knickers, i heard a howl from the kitchen as my mum was stood in the kitchen in tears laughing about the new word.
slowly but surely we are making up our own language