Why was the DUKW called a Duck?

Why did DUKW become Duck, and what did the designation mean?

Duck was the convenient spoken form of a General Motors model code covering the production year, utility role, and driven axle arrangement.

DUKW originated in General Motors model nomenclature and became the spoken nickname Duck. The explanation ties the designation to the 1942 production series, utility use, front-wheel drive, and two driven rear axles. A separate US naval designation, Landing Vehicle Wheeled or LVW, received little use. The shorter nickname proved more memorable.