The word "一意孤行" is formed by the sequential combination of four characters: "一" (one), "意" (mind/intention), "孤" (alone), and "行" (act). The first two characters "一意" together mean "single-minded", and the last two "孤行" mean "act alone", so the phrase literally constructs the concept of persisting in one's own willful course without considering others' opinions.