Where does “tapanhú” come from?

tapanhú (Karirí) comes from Old Tupi tapy'yîuna, from Old Tupi una, from Old Tupi -a, from Old Tupi pó, from Proto-Tupi-Guarani *po, from Proto-Tupian *po — hand.

Ancestry of “tapanhú”, step by step

Step	Language	Word	Meaning
1	Old Tupi	tapy'yîuna	Black person
2	Old Tupi	una	black
3	Old Tupi	-a	forms nouns from a word's stem
4	Old Tupi	pó	hand
5	Proto-Tupi-Guarani	*po	hand
6	Proto-Tupian	*po	hand

Every word from Proto-Tupian *po →Every word from Old Tupi -a →Every word from Proto-Tupi-Guarani *po →