地球
ちきゅう · chikyuu · JLPT N3 · noun
earth
🌍 地球 = ground + ball: the earth is the ball of ground we live on
地 (chi) means ground or land, as in 地図 chizu, map. 球 (kyuu) means ball or sphere, as in 野球 yakyuu, baseball. Ground plus ball gives the planet. Chinese uses the same word: 地球 dìqiú.
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.'
球 — jade radical 玉/王 + qiu 求 (phonetic)
球 is a semantic-phonetic compound. The left side 王 is the 'jade' radical, indicating the original meaning: a fine piece of jade or a jade ornament. The right side 求 supplies the sound 'qiu'. Over time the meaning broadened from a jade sphere to any round object, and today it most commonly means 'ball' or 'globe'.