An Etymological Dictionary of Astronomy and Astrophysics

Optics:
A transparent solid body, having at least two polished plane faces inclined relative to each other, from which light is reflected or through which light is refracted.
Geometry: A solid having two faces lying in parallel planes and with the other faces parallelograms.

Etymology (EN): L.L. prisma, from Gk. prisma, literally “something sawed,” from prizein “to saw.”

Etymology (PE): Manšur, etymology not clear, may be related to Ar. mawšur “prism,” of unknown origin.