墨
すみ · sumi · JLPT N3 · noun
ink
🖋️ 墨 = 黒 black + 土 earth: black dust pressed into ink sticks
The top part is 黒 (black) and the bottom is 土 (earth or soil). Traditional ink sticks were made from soot pressed into a solid block. You may already know the word from sumi-e, Japanese ink painting.
墨 — black 黑 + earth 土
墨 is a semantic compound: 黑 (black) gives the meaning and 土 (earth) refers to the soil-like material. It originally referred to the black ink stick made from soot mixed with binders, used for writing and painting, and later extended to mean ink in general.