Turns out either pronunciation is correct. According to Johnson & Johnson’s website, the original green sticky cloth tape got its name during World War II when soldiers started calling it duck tape for the way liquids seem to roll off like water off a duck’s back.
The company launched a metallic-silver version called duct tape after they discovered it can also be used to seal heating ducts. However, scientists conducted field tests on heating ducts and determined that duct tape was insufficient for sealing leaks or cracks.
Full article: Nguyen, Tuan C. "A Short History of Duct Tape." ThoughtCo, Jul. 31, 2021, thoughtco.com/history-of-duct-tape-4040012.