The word 苏打 (sūdá) is formed through phonetic borrowing, where the two Chinese characters are chosen not for their meanings but primarily for how closely their combined pronunciation approximates the sound of the English word "soda". It is a direct transliteration, capturing the auditory form of the foreign term for "carbonated water" or "sodium carbonate", with its etymology tracing further back through international trade to the Arabic "suwaiḍā" (meaning "headache", as a type of plant ash used medicinally).