The DUKW (colloquially known as Duck) is a six-wheel-drive amphibious modification of the 2.5 ton CCKW trucks used by the U.S. military during World War II and the Korean War.
The name DUKW comes from General Motors Corporation
D, 1942 production series
U, Utility
K, all wheel drive
W, tandem rear axles, both driven
https://en.wikipedia.org/wiki/DUKW