Meaning

adjective of great mass; huge and bulky

originFrom Jumbo (1860–1885), the name given to a large African elephant from East Africa that was purchased in 1882 by American showman P. T. Barnum (1810–1891) for the Ringling Bros. and Barnum & Bailey Circus. Compare Swahili jambo (“matter, thing”) and jumbe (“chief, headman”).

Etymology from Wiktionary, CC BY-SA 3.0