What does Duck mean?

A type of fabric that is known as canvas or plain weave cotton and is created from medium to coarse yarns.

Heddels explains Duck

Also referred to as duck cloth or duck canvas, duck has a wide array of uses, from trousers to sneakers to tents. The name duck comes from the Dutch word “doek”, meaning “linen canvas”. While the fabric tends to be stiff and uncomfortable at first, it becomes wearable after several washes.  Duck is extremely durable and known to be wind resistant.

Additional Resources

Here is a roll of duck fabric:

Heddels Definitions - Duck