'polychromy' originates from Greek, specifically the word 'polukhrōmia' (or 'polychromia'), where 'poly-' meant 'many' and 'khrōma' (chroma) meant 'color'.

'polychromy' passed into Late Latin and French as 'polychromia' / 'polychromie' and was adopted into English as 'polychromy' (via Middle French/Latin influence).

Initially it meant 'the state or quality of being many-colored' (or the use of many colors); over time it came to be used both for the appearance and for the specific artistic technique of multi-colored decoration.