Because "Umbrella" is a Silly Word
You ever wonder how something got its name? Me too. As I was preparing to walk from the car to the store, I found a long-neglected umbrella under the seat and used it, as Tropical Storm Fay would've soaked me through in the 15 second walk. And I start wondering why it's called an umbrella, and then as the word is repeated in my head, it eventually sounds nonsensical, like any word you repeat over and over again. So, I renamed it.