Is it 'duct' or 'duck' tape?

What's the difference between duct tape and Duck Tape®? - Tape University®

Duck 0.75 in. W x 180 in. L Black Solid Duct Tape - Total Qty: 6, 0.75x15ft - Kroger

Duck® Basic Strength Utility Duct Tape - Gray, 1.88 in x 30 yd - Ralphs

Duck Tape 1.88 In. x 15 Yd. Colored Duct Tape, Chrome - Parker's Building Supply

Unicorns Duck brand Duct Tape 1.88 x 10 yard Roll

Duck Brand Basic Strength Duct Tape

DUCK TAPE Duck Tape 222226 Duct Tape, 50m x 50mm, Silver, Gloss Finish

Duck Tape Woodgrain, 10 yd

How Duck Tape Became Famous