late 15c., in alchemy, "transmutation by casting a powder on molten metal; 1550s in the cartographical sense "drawing of a map or chart according to scale," from Middle French projection, from Latin proiectionem (nominative proiectio), from past participle stem of proicere (see project (n.)). From 1590s as "action of projecting."[projection etymology, projection origin, 英语词源]