The story
From Egyptian + blue, from being a blue invented by Ancient Egyptians.
Etymology from Wiktionary, CC BY-SA 4.0.
Egyptian blue
Today it means: A light blue pigment made from calcium copper tetrasilicate (“CaCuSi₄O₁₀”), the first artificial pigment, used by Egyptians for over 3 millennia, before dying out during the Roman Empire; one of the few alternates to lapis lazuli during ancient times. Full definition →