The Chinese word '彻头彻尾' is formed by repeating the character '彻' (meaning 'thorough' or 'to penetrate') in conjunction with '头' (head) and '尾' (tail), creating a symmetrical compound where '彻头' and '彻尾' are combined to literally express 'through head through tail,' thereby conveying the sense of being absolute or complete from start to finish.