What characteristic of a mongoose makes it hard to frighten one and accounts for the mongoose motto: "Run and find out"?

The motto stated in the question comes from Rudyard Kipling's short story "Rikki-Tikki-Tavi." The motto perfectly embodies the central character, Rikki-Tikki. "Run and find out" refers to the natural curiosity of a mongoose. The story says it is nearly impossible to frighten a mongoose because they are so consumed with curiosity. That means when a mongoose comes across something that should be terrifying, the mongoose isn't scared, just more. This holds true in Kipling's story....

The motto stated in the question comes from Rudyard Kipling's short story "Rikki-Tikki-Tavi." The motto perfectly embodies the central character, Rikki-Tikki. "Run and find out" refers to the natural curiosity of a mongoose. The story says it is nearly impossible to frighten a mongoose because they are so consumed with curiosity. That means when a mongoose comes across something that should be terrifying, the mongoose isn't scared, just more. This holds true in Kipling's story. When Nag and Rikki-Tikki first meet, Nag raises himself up and spreads his hood open. The text says Rikki-Tikki was momentarily frightened, but then remembers he used to eat snakes. From that moment his curiosity takes over, and Rikki-tikki begins questioning Nag, not fearing him.