吞吞吐吐 is formed by reduplicating the characters 吞 (meaning to swallow) and 吐 (meaning to spit out) in a sequence where each character is repeated once, creating a four-character compound. This structure emphasizes the alternating actions of swallowing and spitting, which metaphorically translates to describing speech that is hesitant or faltering, as if words are being awkwardly drawn out and retracted.