The word "吹口哨" is formed from three characters: 吹 (chuī), meaning "to blow"; 口 (kǒu), meaning "mouth"; and 哨 (shào), meaning "whistle". These characters combine sequentially to create a verb phrase where 吹 acts upon the compound object 口哨, literally "blow mouth whistle", explicitly denoting the action of producing a whistling sound by blowing air through the mouth.