köken: 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 Esperanto ok Esperanto -a Esperanto dudek-oka From du + dek + ok + -a.