insufficiently-advanced-magic
Nenio only remembers names of things she intends to dispose of shortly. If they're going to figure in her future experiments she gives them a more convenient label like "boy" or "test subject #341".
This thing? Plainly useless. She wouldn't want its pelt for cleaning supplies. She'll be pleased to forget its name in a minute or two.
(It may be relevant that Nenio's Cunning is currently in the region of 30 and she has grasped the entire situation from the context clues well before any of the others managed to formulate the hypothesis of what Wenduag has done. The act is, after all, unthinkable - unless you are very good indeed at thinking clearly.)