Alastor is the one who found it in his own bayou that he had connected to the Hotel. Whether it already lived there or if it managed to get in somehow remains unclear.
He did, however, immediately take a liking to it and it didn’t take long for it to follow him everywhere. Upon finding out how useful it could be he decided to name and keep it.
Alastor usually has it threaten or disembowel people to make a point, the fact that it barely talks helps with the creep factor. He is quite fond of it, feeds it raw meat, and lets it stay and roam the bayou whenever it wants.