Together, 沙 (shā) and 发 (fā) don't create a new meaning from their individual parts. They are simply characters chosen to sound like the English word “sofa.” This is a very common way that foreign words are adopted into Chinese.
The term 沙发 (shāfā) provides a fascinating window into modern Chinese culture, bridging the physical and digital worlds. 1. The Literal Meaning (The Furniture): The adoption of the sofa into Chinese homes represents modernization and the influence of Western lifestyles. A comfortable sofa in the living room is a common feature of a modern, middle-class household, symbolizing leisure, family time, and hospitality. 2. The Slang Meaning (The “First Comment”): This is where 沙发 becomes culturally unique. On the Chinese internet, being the first to comment on a blog post, video, or forum thread is called “grabbing the sofa” (抢沙发 - qiǎng shāfā).
Understanding when to use each meaning of 沙发 is key. The context will almost always make it clear.