1690s, from Latin apodyterium "undressing room" (in a bath house), from Greek apodyterion "undressing room," from apodyein "to put off, undress," from apo- "off" (see apo-) + dyein "to put on, enter, go in."
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for apodyterium
Along the walls were benches, and above them niches, as in the men's apodyterium.
In the generality of modern baths, the frigidarium forms also the apodyterium.
The frigidarium serves also as the apodyterium, and is cut up into divans by ornamental wood partitions.
Similar benches are found in the waiting room at the other end of the apodyterium (X).
The dressing room, apodyterium, was usually entered from the court through a passageway or anteroom.