The idiom "寥若晨星" is formed by combining four characters: 寥 (liáo), meaning "few" or "sparse"; 若 (ruò), meaning "like" or "as"; 晨 (chén), meaning "morning"; and 星 (xīng), meaning "star". Literally, it translates to "as sparse as morning stars", creating a metaphorical comparison where the scarcity of something is likened to the few stars visible in the dawn sky, thus conveying the meaning of extreme rarity or scantiness.