Merriam Webster defines the word like this:
- Main Entry: bum·ber·shoot
- Pronunciation: \ˈbəm-bər-ˌshüt\
- Function: noun
- Etymology: bumber- (alteration of umbr- in umbrella) + -shoot (alteration of -chute in parachute)
- Date: circa 1896
According to this article most people think bumbershoot is an British term for umbrella but the author makes a compelling argument that the origin of this curious word is American rather than British. He says that the word isn't British, since it isn't know in Britain at all. He speculates that people associate it with the English because it was used in a song lyric from Chitty Chitty Bang Bang which was set in England. The song was written by two Americans for the Disney film.
But even before Chitty Chitty Bang Bang, L. Frank Baum used the word in 1912 in his book, Sky Island.
“This umbrella has been in our family years, an’ years, an’ years. But it was tucked away up in our attic an’ no one ever used it ’cause it wasn’t pretty.” “Don’t blame ’em much,” remarked Cap’n Bill, gazing at it curiously. “It’s a pretty old-lookin’ bumbershoot.”
So, now you know!