The word 引擎 is formed through phonetic borrowing, where two existing characters are selected and combined solely for their sound to imitate the foreign word "engine". The characters 引 (yǐn) and 擎 (qíng) were chosen not for their original meanings ("to pull" and "to lift", respectively) but because their combined pronunciation approximates the English source word. This creates a new, purely representational term for a technological concept that did not previously exist in the Chinese lexicon.