1530s, "act of going out," from Latin egressus "a going out," noun use of past participle of egredi "go out," from ex "out" (see ex-) + -gredi, combining form of gradi "step, go" (from PIE root *ghredh- "to walk, go"). Perhaps a back-formation from egression (early 15c.). Meaning "place of exit" is from 1670s. "One who goes out" is an egressor.