Another word for dog in Russian is пёс, which specifically means a male dog. The ё in the latter is a fleeting vowel, so the word declines like this:

There are two well-known созвездия constellations that contain this word, and they are Большой Пёс and Малый Пёс, which mean the Big Dog and the Little Dog respectively. In English we mostly use the Latin names for constellations, and the Latin word for dog was canis; thus we call those constellations Canis major and Canis minor.