The word "吃豆腐" is formed by directly combining the verb "吃" (to eat) with the noun "豆腐" (tofu), resulting in the literal meaning "to eat tofu". This compound then acquired an idiomatic sense through cultural metaphor, where the soft, easily consumed nature of tofu symbolizes vulnerability, leading to the extended meaning of taking advantage of someone, often in a sexually suggestive or harassing context.