疲

Outer sickness radical - a stylized bed-on-its-side with a person leaning against it, picturing someone laid up ill. The indexing radical, files 疲 in the family of illness/symptom chars: 病 illness, 痛 pain, 疼 ache, 疾 disease, 痕 scar. Marks fatigue as a body's near-pathological state, treated by classical medicine as something to recover from.

Inner 皮 supplies the sound - pí exactly, no shift. The 'skin' meaning adds a faint semantic flavor: exhaustion that shows on the surface, in the face and limbs. Same phonetic family: 彼 that one, 被 by / quilt, 波 wave, 玻 glass, 破 broken. Mnemonic: when ill (疒) and your skin (皮) is dragging - you are 疲 tired.