Tendon remodeling for impact absorbtion
One of my best kinesiology and sports medicine instructors also does a lot of instruction at the local circus school - and he noted that folks who do lots of trampoline training end up with stronger tendons and are capable of taking impacts (including on hard surfaces) far better than the average person.
So far science points to tendons strengthening under lots of high repetition exercises, or continuous stress over time... so the repeat impacts of trampoline would seem to be creating those conditions (probably along with people becoming better at body mechanics in taking impact as well).
Obviously, however, you will need access to a trampoline and preferably skilled instruction, as trampoline accidents and injuries from people just setting one up and going at it are relatively high.
A different way at getting at this effect which I've only recently encountered is high velocity, low weight loading from catching thrown objects. The Sikh martial art Shastar Sanatan Vidiya demonstrated this using thrown iron balls or tossing up and catching a spear or staff a few inches, over and over, so that the downward weight pulls on the tendons in the spine.
I have only gotten to practice this a little bit, and it's unquestionable that the back muscles are activated for this, and it seems in line that it would lead to tendon strengthening, but I haven't had the months/years of practice to talk about larger effects and whether the effect in taking force better is worth the time invested.
Ground Tumbling, Pratfalls
Falling happens in fighting. Along with the usual styles that teach falling techniques, there's a variety of tumbling activities ranging from acrobatics, "movement play", parkour, some dance moves, and clown pratfalls.
While these tend to have some similarities they also have some differences mostly in the types of falls they expect, how one is expected to come out of the fall and exercises for practice. Nonetheless, I'd say it's worth looking at these to see what's worth taking and what won't work for your goals.