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, comb. form of gradi "step, go" (see grade, n.). Perhaps a back-formation from egression (early 15c.). Meaning "place of exit" is from 1670s. "One who goes out" is an egressor.