In traditional Chinese philosophy, a person has two types of soul: 魂 (ethereal soul that ascends after death) and 魄 (corporeal soul tied to the body). Together 魂魄 means the complete soul.
usage
Rarely used alone. Most common in compounds: 气魄 (boldness), 魂魄 (soul), 魄力 (courage/daring), 落魄 (down and out).
鬼 (ghost / spirit) is the indexing radical. In Chinese folk metaphysics a person has two souls: the cloud-soul 魂 that floats off at death and the bodily soul 魄 that stays with the corpse - both written with the ghost radical. 魂魄 names the pair.
白 supplies the sound, drifted to pò. There's a quiet semantic flavour too: the 魄 was traditionally the moonlight-pale soul of a person (as opposed to 魂, the cloud-like wandering soul), so the white element fits. Same phonetic series: 拍, 泊, 伯, 帕.
