Where does “tĩta” come from?

tĩta (Old Portuguese) comes from Latin tincta, from Latin tingere, from Proto-Indo-European teng- — to think.

Ancestry of “tĩta”, step by step

Step	Language	Word	Meaning
1	Latin	tincta	nominative feminine singular of tīnctus;...
2	Latin	tingere	second-person singular future passive indicative...
3	Proto-Indo-European	teng-	to think