how people keep bread-starter before fridge invented?
I imagine there was no need to store it because bread was being baked every day so it would be fed daily for that day's bake.
If you feed a moist/liquid starter once or twice a day, you don't need to refrigerate starter at all. If you don't bake every day, keep just a very small amount, and build it up with feeding, so that when baking day comes around, you have enough to bake with, and with just a tiny amount left over to carry forward and build up to the next time.
Another method is to not keep a moist/liquid starter, but a firm starter, sometimes called a "biga" which does not have to be fed every day. My Italian friend's mother and grandmother used the biga method.
I also heard that people in the olden days would keep stiff starters submerged in either flour or salt to dry out the yeast and cause them to go dormant. When they wanted to make bread, they would just crack open the dry starter, scoop out the stuff in the middle, rehydrate it, and wait for the yeasts to wake up again.