Just thought I'd mention it...I have no idea what sparked the idea of having a giant intelligent otter.
I think it was an exceptionally lazy and formulaic method of designing monsters intended to flll pages when minds had otherwise blanked. Some of these combinations worked out (e.g., owlbear), but I personally think that a great many more of them were. . . well. . . dumb. I mean, there's a reason that the Giant Lynx isn't immediately associated with D&D.
She had intelligent, telepathic cats in several books that predated the Witch World series. (The first book of hers I ever read, Star Man's Son/ Daybreak 2250 AD, had one. Copyright 1952!)Andre Norton's Horn Crown came out in 1981, which makes it a bit iffy as a potential source, but maybe there was one in another Witch World book that came beforehand.
The actual facts don't make this clear. First of all, the owlbear was a well-known result of Gygax statting up a plastic toy (along with the rust monster and bulette).
Don't remember lynxes, but MM 1e also has giant intelligent beavers IIRC.