Pop is a concession, a retreat, a capitulation to the massive marketing machines of modern commerce. It began as a branding effort, while soda is descriptive of the chemical properties involved. Do not give in the the manipulation of corporate interests, even those whose roots are over a century old! (The abominable practice of others to call all sodas, generically, "coke" is similarly flawed although that name at least, in addition to marketing, has some basis in the chemical makeup of the drink that began its inception)