Etymology tree Esperanto du Proto-Indo-European *déḱm̥ Proto-Hellenic *dékə Ancient Greek δέκα (déka)der. Proto-Indo-European *déḱm̥ Proto-Italic *dekəm Latin decemder. Esperanto dek Proto-Afroasiatic *sṗɣ? Proto-Semitic *šabʕ-bor.? Proto-Indo-European *septḿ̥ Proto-Italic *septəm Latin septembor. Esperanto sep Esperanto -a Esperanto dudek-sepa From du + dek + sep + -a.