Where does “tayú” come from?

tayú (Karirí) comes from Old Tupi itaîuba, from Old Tupi îub, from Proto-Tupi-Guarani *juβ — yellow.

Ancestry of “tayú”, step by step

Step	Language	Word	Meaning
1	Old Tupi	itaîuba	gold
2	Old Tupi	îub	to lie
3	Proto-Tupi-Guarani	*juβ	yellow