Lentorama 2013: There's a Name for That

Day 15: pyx

The pyx is a small, round container used to transport consecrated hosts to the sick or other people unable to go to mass. In some cases the pyx is put into a special case called a burse, which is made out of a fabric or leather and worn so that the pyx and the hosts inside do not get lost.

The term is also used to describe any small box or holder, and its name suggests that early models were made of boxwood (modern pyxes are made of metal, typically). The glass-walled insert that holds the host in a monstrance or other display can also be called a pyx, though you wouldn't cart it around to give communion.