下地
したじ · shitaji · JLPT N1 · noun
basis
🧱 下 = under + 地 = ground: the ground laid underneath, so groundwork
The reading したじ comes from 下 (shita, under) and 地 (ji, ground). Together they name the base layer that everything else is built on.
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'.
地 — earth 土 + 也 (phonetic)
地 is a semantic-phonetic compound. The left component 土 means 'earth' or 'soil' and gives the meaning, while 也 on the right hints at the pronunciation. Originally referring to the ground or land, it broadened to mean 'place,' 'region,' and 'territory.'