Area above shower

I have decided to redo a bathroom off of my kitchen and make it into a pantry. I am taking out the multiple layers of drywall, but they seem to be under this section and I have no idea why this is here/what it is for. Any guesses are appreciated. There is a room above it, but nothing showing why this would be down like this. This is a big project, I just don’t want to make it bigger by taking it down if it’s important.