In Japan, when thunder starts, adults sometimes tell children, “Hide your bellybutton,” or “The thunder god will take it.” It comes from an old folk belief that the thunder god descends from the sky and steals people’s bellybuttons—a story that is a little frightening and a little funny at the same time.
Of course, most parents and children today do not literally believe that a thunder god is coming for anyone’s bellybutton. Children may understand that it is mostly a joke and still instinctively cover their stomach with their hands when they hear thunder. Even while thinking, “That can’t really happen,” they may hide it anyway. That strange mixture of disbelief and reaction is part of why the saying has remained so familiar in Japan.
There are several explanations for why children were told to hide their bellybuttons in the first place. One says that thunderstorms can bring a sudden drop in temperature, so adults wanted children to keep their stomachs covered and avoid getting chilled. Another says that the warning encouraged children to stop playing outside and move somewhere safer when thunder approached.
It is difficult to say with certainty that either explanation was the original reason. Whatever its original purpose, though, the phrase certainly gets a child’s attention. Hearing that the thunder god might take their bellybutton is memorable enough to make a child cover their stomach or pay closer attention to the storm.
What makes the custom especially interesting today is that many parents who use the phrase do not know why people started saying it. They heard it from their own parents as children, so when thunder comes, the same words simply come out naturally. Some adults may even use the phrase with their own children and only later learn that practical explanations have been attached to it.
This is not usually something children formally learn from teachers at school. It is closer to an old family expression that has survived in everyday life. That is why saying, “The thunder god will take your bellybutton,” does not necessarily sound especially old-fashioned, even today.
The saying survives not because Japanese people still seriously believe in a thunder god, but because people repeat to their children what they once heard from their own parents. Even after the original reason becomes unclear, the words themselves remain. In that way, an old superstition continues to live quietly inside ordinary family life.
