Green’s Dictionary of Slang

(US) an umbrella.

1861		(con. 1840s–50s) H. Mayhew London Labour and the London Poor I 368/1: These I should have at my back, and the remainder of my chany and glass on my head, and werry probably a bumberella or two under my arm.
1905		L. Pound ‘Dialect Speech in Nebraska’ in DN III:i 60: bumbershoot, n. Umbrella, or parasol.
1934		Weseen Dict. Amer. Sl.
1947		M. Henry Sea Star (1991) 150: I’d be combin’ his curly mane with my fingers and feelin’ of the little ribs stickin’ out like the ribs of Grandma’s bumberella.
1968		Dahl & Hughes Chitty Chitty Bang Bang [film script] Me ol’ bam-boo, me ol’ bam-boo / You’d better never bother with me ol’ bam-boo / You can have me hat or me bumbershoot / But you’d better never bother with me ol’ bam-boo.