"Jokisen" was a product name of high-quality green tea, and as cups of strong green tea excite drinkers, this poem satirized those who were frightened and worried by just four jokisen (steam boats) from foreign countries.
上喜撰とは玉露茶の商品名で、濃茶を飲むと興奮するように、たった四隻の外国船（蒸気船）に驚き、心配になることを風刺した。