Rancor

Star Wars Lore
Rancors are rare creatures, found only on scattered worlds such as Dathomir and the Ottethan system. The rancors of Dathomir are stronger and much more intelligent than others. They have even been domesticated by the Witches of Dathomir, though it is likely that only beings as powerful in the Force could ever hope to successfully tame a rancor.

No one is quite sure where Jabba's rancor came from, since the planet Dathomir is under a strict quarantine that prevents anything from leaving the planet. The rancor was discovered in a starship that had crashed in the Tatooine wastes. The ship belonged to a Captain Grizzid, a trader of some notoriety that had dealt with Jabba in the past. Jawas approached one of Jabba the Hutt's many lieutenants, Bidlo Kwerve, with information of a new salvage site containing a deadly predator. Intrigued, and trying to curry favor with the Hutt, Kwerve organized an inspection party to visit the site.

Kwerve and his Gamorrean crew reached the wreck, and after much bloodshed, managed to incapacitate the creature inside. Bib Fortuna, Kwerve's main rival, arrived at the site, demanding to know what was going on. Three days later, Fortuna and Kwerve presented the rancor as a gift to Jabba. Fortuna was promoted to chief lieutenant of all of Jabba's operation while Kwerve was honored as being the rancor's first meal at Jabba's palace. Jabba entrusted the care of the rancor to a Corellian named Malakili, who loved the beast as a cherished pet.