* "Bumbers" likely refers to a "bum" or "bottom," implying the umbrella's ability to protect the bottom of the user from rain.
* "Shoot" is a bit less certain, but it might be a playful alteration of "shoot out" or "shoot up," suggesting the umbrella's action of pushing away rain.
Therefore, "bumbershoot" might be interpreted as "a thing that shoots rain away from your bum."
There are other theories as well, but this one is the most widely accepted.
It's important to note that "bumbershoot" is considered an archaic and somewhat humorous term for an umbrella. It was popular in the 19th century but is rarely used today.