脾

Left flesh radical - the meat-form of 肉, visually identical to 月 (moon) but distinct in meaning. Anchors 脾 in the body-organ family: 肝 (liver), 肺 (lung), 肾 (kidney), 胃 (stomach), 胆 (gallbladder). The radical states 'this is a fleshy internal organ'. The spleen sits firmly in the catalogue of bodily organs that take the meat-radical prefix.

Right 卑 supplies the sound - bēi shifted to pí, regular b/p labial alternation. 卑 originally pictured a hand holding a ladle, a marker of a low servant's role; that meaning doesn't carry. Same phonetic family: 啤 (beer), 婢 (slave-girl), 牌 (sign/plaque), 碑 (stele). Common compound 脾气 (pí qì, temperament) reflects the classical theory of the spleen as the seat of mood and disposition.