image via The Coca-Cola Company
Coca-Cola was first bottled in 1894. In those days Coke bottles were different than they are today, and far less sanitary. In 1879, Charles G. Hutchinson invented what became known as the Hutchinson Bottle. These early curiosities were squat six-ounce bottles which sealed by means of a rubber gasket. This gasket, which looked like a rubber washer, was sandwiched between two iron plates, and a long metal hook was attached to the top plate. A seal could be formed because the gasket, which was slightly larger in diameter than the bottle's opening, remained inside and pushed up against the shoulders while the hook extended through the mouth. The carbonation was supposed to push the gasket up against the inner shoulders and seal the mouth of the bottle, but it didn't work very well. The bottles leaked and, according to reports at the time, the rubber washers made the drink taste bad. In order to open a bottle, one had to push the hook and gasket down into the drink, which couldn't have been very sanitary either. I've heard it said that releasing the seals on these bottles made a "popping" sound, which is, supposedly, how the word "pop" originally became synonymous with bottled soda.
hat tip: Scribal Terror