Where does “διάδημα” come from?

διάδημα (Koine Greek) comes from Ancient Greek διαδέω, from Ancient Greek δῐᾰ-, from Ancient Greek διά, from Proto-Indo-European dwís, from Proto-Indo-European dwóh₁ — two.

διάδημα (Koine Greek): a decorative wreath-shaped headdress; headband;...