The whole shape is a fused remainder of the traditional form
喪, which stacked two mouths over
衣 (clothing) - mourners weeping around a funeral garment. Simplification compressed it all into one block, but the bottom
亡 (to perish) still carries the core: every reading traces back to loss. Indexed under Kangxi #1
一 (yī, one) by tradition; the radical is not separable in the modern form.
