The word "唧唧" is formed by reduplicating the single character "唧", which is itself a phono-semantic compound character composed of the semantic radical "口" (kǒu, meaning 'mouth' or related to sound) and the phonetic component "即" (jí, indicating pronunciation). This duplication creates a disyllabic onomatopoeic term that typically represents repetitive sounds, such as chirping or rustling.