The mirror of 上: baseline with a stroke hanging beneath. Together they're the yin-yang of position — the first abstract concepts a script ever drew, needing no object at all, just relation.
下 works as hard as 上: 下班 get off work (the day's sweetest verb), 下雨 it rains ('rain descends'), 下次 next time, 下载 download. 天下 'all under heaven' was the classical word for the world itself — everything below the sky was the empire's concern.
A root growing BELOW the line — DOWN.
下饭 'goes down with rice' praises any dish that makes you eat more rice — and now describes bingeable shows: 下饭剧, TV to eat by.