A childhood belief about skin

A few days ago, it was a friend's birthday, and I jokingly commented, "I hope he doesn't come to school in his birthday suit." My boyfriend looked blankly at me and said, "We have to wear uniforms. He can't wear a special outfit because it's his birthday!" After taking my boyfriend aside and explaining that being in your birthday suit meant being naked, he looked very embarassed. He's a senior in high school, and he thought until that day that a birthday suit was a special outfit that you only wore for special occasions.