Oscilla

Oscilla is a word applied in Latin usage to small figures, most commonly masks or faces, which were hung up as offerings to various deities, either for propitiation or expiation, and in connection with festivals and other ceremonies.

As the oscilla swung in the wind, oscillare came to mean to swing, hence in English oscillation, the act of swinging backwards and forwards, periodic motion to and fro, hence any variation or fluctuation, actual or figurative.

[1] Many oscilla or masks, representing the head of Bacchus or of different rustic deities, are still preserved.

Others still in existence are made of earthenware, but it seems probable that wax and wood were the ordinary materials.

Small rudely shaped figures of wool, known as pilae, were also hung up in the same way as the oscilla.