@AEnigmatrix@fform@coystags More specifically, it's originally a Chinese creature called "mo", based on said Malayan tapir. Though it was an apotropaic creature, the dream-eating part is unique to the Japanese counterpart. Still, it's said that those who sleep on a baku's pelt will never get sick, which does have something of the Chinese original.
@Shita-kiri_Suzume A lot of manga have these types of dream eating monster. Elf-san and sleeping princess come to mind. Both of them use the design of what a normal irl tapir look like, too