The Lost Opposite of Brown Nuts

My nephew is two years old, and he seems to have a basic understanding of opposites. It's interesting to see how he perceives the world, and it's fascinating to hear his responses when he's thrown challenges from Left Field.

Q: What's the opposite of black?
A: White.
Q: What's the opposite of day?
A: Night.
Q: What's the opposite of Christmas?
A: Bad baby!!!

Unfortunately, I've forgotten which of my queries elicited the response "brown nuts!" I guess we'll have to add it to the list of unfortunate holes in the vast tapestry of human knowledge.