Etymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Hellenic *ə- Ancient Greek ἀ- (a-)der. English a- Proto-Indo-European *sek-der. Proto-Indo-European *séks-u-sder. Proto-Italic *seksus Latin sexus Proto-Indo-European *h₂el-der.? Proto-Italic *-ālis Latin -ālis Latin sexuālisbor. English sexual English -sexual English asexual From a- (“lacking, without”) + -sexual.