下痢
げり · geri · JLPT N1 · noun
diarrhea
🚽 下 (down) + 痢 (dysentery) = the illness where things come down fast
痢 combines the sickness radical 疒 with 利 as its sound part. 下 means down, so 下痢 names the 'downward flux' of watery stools.
下 — horizontal line 一 + mark below
下 is an indicative character: a long horizontal line represents a reference level, and a shorter stroke placed beneath it points to the area below. The original meaning 'below, down' comes directly from this spatial diagram, and it later extended to verbs like 'descend' and 'lower'.