the moving creatures: small animals named for how they go, gliding or scurrying low to the ground
This word picks out a group of animals not by what they are but by how they move. It comes from a verb that means to creep, glide, or stir, the kind of low, brushing, scurrying motion a small creature makes close to a surface. So the noun gathers up "the moving ones," the little animals that get about by creeping rather than by walking tall or flying. English Bibles almost always say "creeping things," which is close but a bit narrow; "the moving fauna" or "things that go low" catches the idea better.
In the creation account the word has a fixed, almost technical place: it names the small ground-animals as one of three kinds of land creature, set beside the livestock and the larger wild beasts. The same tidy listing turns up wherever the Bible surveys the animal world, for instance in the note about Solomon's knowledge of nature, or in the songs that call every kind of creature to praise God.
The word can also stretch well past that narrow slot. After the flood it widens to cover every living thing that moves, when God gives "every moving thing that lives" to people for food. In poetry it reaches further still: it can name the countless small creatures swarming in the sea, and in one stark image it pictures human beings reduced to creatures that creep along with no one to rule them. Across all these uses the thread that holds is the motion, not the species: the word keeps meaning "the ones that move low," whether they are insects on the soil or shoals in the ocean.