The word "火眼金睛" is formed by directly combining the two-character terms "火眼" (fire eyes) and "金睛" (golden pupils), originating from the depiction of Sun Wukong in "Journey to the West" to describe his perceptive ability. The formation uses the literal attributes of fire (penetrating illumination) and gold (valuable clarity) to create a metaphorical compound meaning exceptionally sharp or discerning vision.