The word 唉声叹气 is formed by combining the two-part phrases 唉声 and 叹气: 唉声 pairs the interjection 唉 (sigh) with 声 (sound) to mean "sound of a sigh", while 叹气 pairs 叹 (sigh) with 气 (breath) to mean "to sigh". Joined, they create a four-character idiom that literally denotes producing sighing sounds and exhaling in lament, directly illustrating the action of sighing with disappointment or sorrow.