What is the X in X-mas?
1520s, from Latin evacuatus, past participle of evacuare "to empty, make void, nullify," used by Pliny in reference to the bowels, used figuratively in Late Latin for "clear out," from ex- "out" (see ex-) + vacuus "empty" (see vacuum).
Earliest sense in English is medical. Meaning "remove inhabitants to safer ground" is from 1934. Replaced Middle English evacuen (c.1400). Related: Evacuated; evacuating.
evacuate e·vac·u·ate (ĭ-vāk'yōō-āt')
v. e·vac·u·at·ed, e·vac·u·at·ing, e·vac·u·ates
To empty or remove the contents of.
To excrete or discharge waste matter, especially of the bowels.