Where does “Tocantins” come from?

Tocantins (English) comes from Portuguese Tocantins, from Old Tupi tukã, from Proto-Tupi-Guarani *tũkãn.

Ancestry of “Tocantins”, step by step

Step	Language	Word	Meaning
1	Portuguese	Tocantins	—
2	Old Tupi	tukã	Toucan
3	Proto-Tupi-Guarani	*tũkãn	—

Tocantins — Etymology, Origin & Word History | Etymology Explorer