You Learn Something Every Day: Duct Tape vs. Duck Tape
When American troops fought World War II, thousands of rolls of “duck” tape went with them. Although it’s now called “duct” tape, back then it was duck tape.
During the war the army needed a strong waterproof tape to keep moisture out of ammo boxes. Johnson & Johnson created it, and because it was waterproof, everyone called it “duck” tape — as in water off a duck’s back. Soon troops were using it for everything from making jeep repairs to patching leaky tents. Some say it helped win the war.
It became duct tape when, later on, many soldiers went into the housing industry and duck tape went with them. They found it was great for joining ductwork; soon good old Army green evolved into the silver tape we have today. So calling it either duct tape or duck tape is correct and acceptable.