The bungee cords I buy are elastic strands with a woven/braided cover and a hook at each end. There is even a "sport" called bungee jumping where you jump off of high places with elastic bands tied to the feet.
As I study on finger weaving and braiding, usually braiding is done around a rope or cord to prevent stretching. Apparently one can braid around elastic bands, Then when the elastic stretches the woven cover stretches with it. With some experimentation someone could determine the best weaving angle or pattern for the cover.
It's interesting to see how things are put together. I've used bungee cords to tie down tarps and hold gates open/closed and only now understand the construction of the bungee cord.
It's not a terribly important detail, but it is one more thing I understand as a result of the fiber adventure.
Have a good day!