In the early 2370s, they lost everything when their world was assimilated by the Borg, except for 27 ships. These escaped carrying a small number of survivors but were forced to wander throughout space, begging where they could, but more often than not being driven off.
By early 2374, the situation of the survivors was desperate. Malnutrition was common, which took an especially hard toll on the children. Attempts to settle on a planet, where they could grow their own food, failed as they were seen as vagrants, even criminals, and unwelcome. That year, a group of three Caatati ship encountered the USS Voyager and were given stocks of food. A little later, they found Voyager's warp core after it had been dumped and claimed it. They then tried to use it as a bargaining chip for more supplies.
Instead, Seven of Nine offered them the lost thorium replication technology, which she recalled from her time with the Borg. The Caatati gladly agreed. (VOY: "Day of Honor")