The word "瓶盖" is formed by combining the character "瓶", meaning bottle, which itself is a pictophonetic character with the radical "瓦" indicating pottery and the phonetic component "并" suggesting pronunciation, and the character "盖", meaning lid, also a pictophonetic character with elements historically denoting a cover over a vessel. Together, they create a compound noun where "瓶" modifies "盖" to specify a bottle lid.