evacuee (n.)

1520s (trans.), 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 assimilated form of ex- "out" (see ex-) + vacuus "empty," from PIE *wak-, extended form of root *eue- "to leave, abandon, give out."

Earliest sense in English is medical. Military use is by 1710. Meaning "remove inhabitants to safer ground" is from 1934. Intransitive sense is from 1630s; of civilian persons by 1900. Replaced Middle English evacuen "draw off or expel (humors) from the body" (c. 1400). Related: Evacuated; evacuating.

word-forming element in legal English (and in imitation of it), representing the Anglo-French -é ending of past participles used as nouns (compare -y (3)). As these sometimes were coupled with agent nouns in -or, the two suffixes came to be used as a pair to denote the initiator and the recipient of an action.

Not to be confused with the French -ée that is a feminine noun ending (as in fiancée), which is from Latin -ata.