Where does “θετικός” come from?

θετικός (Ancient Greek) comes from Ancient Greek θέσῐς, from Ancient Greek τίθημι, from Proto-Indo-European dʰeh₁- — to do, put, place.

θετικός (Ancient Greek): fit for placing, apposite; concerning adoption;...

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	θέσῐς	arrangement, placement, setting; conclusion,...
2	Ancient Greek	τίθημι	I put, place, set; I make, cause to be; I make
3	Proto-Indo-European	dʰeh₁-	to do, put, place