c.1400, "a box," especially the vessel in which the host or consecrated bread is preserved, from Latin pyxis, from Greek pyxis "box-wood; a box," from pyxos "box-wood; box-tree," of uncertain origin.
in Christianity, vessel containing the consecrated bread used in the service of Holy Communion. Although pyxes were made in various shapes, such as that of a dove, the most common form was that of a small, cylindrical box fitted with a cover, which is generally conical. An English pyx dating from the first half of the 14th century, known as the Godsfield Pyx, is of gilt bronze with engraved foliage decorating the lid and body. Another well-known English medieval example is the Swinburne Pyx (c. 1310); a small, circular box fitted with a flat lid, it is silver gilt, with traces of translucent enamel. Changes in the liturgy of the church led to the pyx being placed upon a stand; this form is probably the predecessor of the monstrance, a vessel in which the host is exposed. The few pyxes surviving from the 17th and 18th centuries are usually flat and cylindrical