One day my coworker messaged me saying that she purchased "duck" tape for emergencies. I corrected her saying that it should be "duct" tape. That same day, I went to a crafts store and saw that they sell "duck" tape. Out of curiosity, I googled "duck tape vs duct tape".
It turns out that both names are appropriate.
"Duck" tape was first manufactured during WWII when the military needed a waterproof tape. Everyone referred to it as "duck" tape, because it is waterproof like a duck's feathers.
After the war, it was discovered that the tape was also great for joining heating and air conditioning duct work (special duct tape, not the common duct tape). The color of the tape was changed from the original army green color to silver and people started to refer it as "duct" tape.