The poem is a list of instructions for how to behave when you have no power: scratch your head, bite your tongue, grin, bow low, keep your hands tied and your feet together. Each gesture is a small act of humility or silence, the body of someone who has learned to please, to hold back, and to stay put.
Then a voice asks, "What's all this?" The answer is blunt: ask the belly. Hunger, the poem suggests, is the real reason for all this grovelling. The speaker doesn't say it directly, and that restraint makes the point sharper. Nobody needs to explain the humiliation when the stomach already knows.
The mood is bitter and wry. The short lines move quickly, almost like orders, and the forced grin hints at shame hiding under politeness. The speaker seems less angry at the person bowing than at a world where survival demands it.