A childhood belief about eating

When my sister and I were little, my Mum warned us we had to eat properly at the 5 course dinner we had every Christmas. She told us that if we would chew with our mouths open, or spit something out we didn't like, my uncle would throw up. Last year my uncle died. After the funeral my Mum, my sister and I were talking about our memories of him, and my sister and I said that he must always have had a weak stomach, because something small like people chewing with their mouths open would make him throw up. My Mum suddenly had to leave the room, and when we followed her to see if she was all right, we found out that she was laughing her head off. Somehow it had never occurred to my sister (31) and me (33) that my Mum just invented this throwing up story to make us behave ...