1620s, "act of selecting," from Latin selectionem (nominative selectio) "a choosing out, choice, selection," noun of action from past participle stem of seligere (see select (adj.)). Meaning "thing selected" is from 1805. Biological sense is from 1837; applied to actions of breeders (methodical selection), hence its use by Darwin (natural selection; 1857). French sélection is a 19c. borrowing from English.
1590s, "act of surviving; continuation after some event," from survive + -al (2). Phrase survival of the fittest (1864) was used by Spencer in place of Darwin's natural selection.
