Origins
Every creature is, by its own etymology, something that has been created.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ The word comes from Late Latin creΔtΕ«ra, meaning 'a created thing', from creΔre β 'to make, to produce'. In medieval Christendom, this was not metaphor: a creature was a being brought into existence by God. Humans were creatures. Angels were creatures. Every living thing was a creature of its Creator.
The narrowing to 'animal' happened gradually in English. By the 16th century, creature increasingly referred to non-human living things, especially unfamiliar or strange ones. Horror fiction accelerated this: a 'creature' now often implies something monstrous or alien.
Proto-Indo-European Roots
The Latin root creΔre traces to Proto-Indo-European *αΈ±erhβ- meaning 'to grow'. This connects creature to a wide family: create, creation, creative, increase (to grow into), and Ceres, the Roman goddess of agriculture and growth.
Spanish criatura preserves the older breadth: it means both 'creature' and 'young child'. A baby is the most recently created creature. The word 'creature comforts' also retains theological overtones β comforts of the body, pleasures given to created flesh rather than the eternal soul.