My grandfather called his horses either by normal human forenames, John or by place names, the Place where they were bred or purchased. When he went to war and kept a diary, it was noticeable that his friends also had horses called by human forenames or names from myths and stories.
The strangest naming pattern I have seen is the name Mouse so widely used in the American West for tough mules and quarter horses. Mouse is the hero horse in the novel Lonesome Dove by Larry McMurphy.