Probably ultimately from Proto-Indo-European*h₁eǵʰs-to- (compare Ancient Greek ἐκτός(ektós, “outside”)), suffixed form of *h₁eǵʰs, whence Latin ex (compare also extra, exter from *h₁eǵʰs-tro-, *h₁eǵʰs-ter), Ancient Greek ἐξ(ex), Old Church Slavonic из(iz). Compare the now obsolete Albanian ith, probably from *h₁eǵʰs, and ish derived from a variant form *eḱs.