Where does “亡” come from?

亡 (Chinese) comes from Proto-Sino-Tibetan maŋ, from Proto-Sino-Tibetan *(s/r)-ma(ŋ/k).

Ancestry of “亡”, step by step

Step	Language	Word	Meaning
1	Proto-Sino-Tibetan	maŋ	big; old; elder
2	Proto-Sino-Tibetan	*(s/r)-ma(ŋ/k)	—

亡 — Etymology, Origin & Word History | Etymology Explorer