The word "蹭蹬" is formed by the conjunction of two characters, "蹭" and "蹬", which individually mean to rub/scrape and to step/pedal respectively, but in this compound they function phonetically rather than semantically. Together, they create a disyllabic word where the sounds combine to evoke the meaning of experiencing setbacks or stumbling, with the overall meaning emerging from the phonetic pairing rather than the literal meanings of the separate characters.