there exist many stable expressions which include possessive adjectives following either of the two declensions shown above: (noah's ark, from "noah"), (euclidean geometry, from "euclides"), (the field of mars), (the augean stables, from "augeas"), (a wolfish appetite, from "wolf"), (crocodile tears, from "crocodile"), (every god-given day, from "god"), etc. notice how the latter two differ from the general rule: has ending as if a crocodile were a male human, and has ending as if god is treated as an animal or (in old russian) a crowd (perhaps, symbolizing holy trinity).