"饥不择食" is formed by sequentially combining the characters 饥 (hunger), 不 (not), 择 (choose), and 食 (food) to create a literal meaning of "when hungry, one does not choose food". This arrangement establishes a direct cause-and-effect relationship, where the condition of hunger leads to the action of non-selectivity, resulting in a fixed idiomatic expression used to depict necessity overriding choice.