I chose to break up the name of this particular monster into two words. If I’d called it “Otterman” you might have misread and thought I was talking about the piece of furniture, or the Turkish/Muslim Empire from which the footstool was named. (The muckety-mucks of the Ottoman Empire tended to use such footstools, hence the naming, FYI. Also, turkeys are named after Turkey because of the mistaken belief that they originated there when in fact they are indigenous to North America. Blame Columbus.) In addition, there is no one single Otter Man. There are many. Probably. If they exist at all outside of folklore.
The actual name for the Otter Man is Kushtaka, aka Kooshtakaa, a creature from the mythology of several Indian tribes of the American west coast. In Alaska they are known as Urayuli and are said to be benevolent, or at least indifferent, to humans. The Kushtaka, however, is sometimes malevolent. In Alaska, the beings tend to appear only in the shape of the traditional Sasquatch or Bigfoot, whereas they can assume other forms as the Kushtaka. One of those forms must at least somewhat resemble an otter, although they might be likened to an otter because of their association with the water, ala the Skunk Ape of the American South.