Where does “diadēma” come from?

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

diadēma (Latin): diadem, crown, tiara; a royal headdress