Whipcord is the name for either a fabric or a form of braided cord.
Whipcord is usually found in durable outdoor clothing (typically pants, sometimes jackets) as a 16 to 18oz (ounces per square yard of fabric) wool, or in durable workers' clothing (typically overalls) as a 9 to 12oz cotton. In the latter case, whipcord is an alternative to duck, which has a different weave.
Cord
Whipcord (also "whipcording") is a form of cordage used to make whippings, secure knottings placed over the ends of ropes to keep them from fraying. Sometimes called Interlocking, it is made by plaiting together four strands to make a stronger cord, usually using bobbins to weight the strands and make them easier to control.
It can be worked as a solid color or in a stripe or a diagonal for a two color pattern.