The word "蹩脚" is formed through a metaphorical compound, combining the character "蹩" (bié), which originally means to sprain or limp, suggesting something strained or awkward, with "脚" (jiǎo), meaning foot. Together, they create a vivid literal image of a limp or unsteady gait, which is then extended metaphorically to describe anything that is shoddy, inferior, clumsy, or poorly executed, much like the unstable movement of an injured foot. This semantic shift from a physical ailment to a qualitative judgment exemplifies a common pattern in Chinese word formation where concrete sensory experiences are used to express abstract qualities.