words related to number "eighteen":
Greek word DEKAOKTW means "eighteen", and DEKATOS OGDOOS means "eighteenth",[Divry's Modern English-Greek, Greek-English Dictionary, 1988, p. 762].
Turkish cardinal numeral for "eighteen" is "ONSEKIZ" and for ordinal numeral "eighteenth" is "ONSEKIZINCI".
a) When the Greek word DEKAOKTW, meaning "eighteen", is rearranged in two parts as "DEKA-OKTW", we have the terms DEKA and OKTW which were explained under Item 12 -Greek words related to number "ten" and under Item 10 - Greek words related to number "eight" respectively. There we found that DEKA was part of Greek words which were made up from Turkish expressions that used Turkish numeral ON meaning "ten", and OKTO was part of Greek words which were made up from Turkish expressions that used Turkish numeral SEKIZ meaning "eight". Thus, the Greek cardinal numeral name DEKAOKTW has been fabricated from Turkish cardinal numeral "ONSEKIZ" meaning "eighteen", but in a disguised and convoluted way.
b) The Greek ordinal numeral DEKATOS OGDOOS corresponds to Turkish ordinal numeral "ONSEKIZINCI". On the surface, there is no resemblance between these two numeral names belonging to different languages. In this Turkish numeral name, the Turkish ON means "ten", SEKIZ means "eight" and SEKIZINCI means "eighth" , ONSEKIZ means "eighteen", ONSEKIZINCI means "eighteenth" where suffix "INCI" corresponds to the English suffix "th".
At this point, we must remember that the Greek term DEKATOS meaning "tenth" also has the form DEKATON meaning "tenth", [Divry's dictionary, p. 468]. This makes the composite Greek numeral name DEKATOS OGDOOS as DEKATON OGDOOS.
Now, when the Greek composite name DEKATON OGDOOS, meaning "eighteenth", is rearranged letter-by-letter as "ON-SEKASODGODO-T" or "OD-SEKASONGODO-T", we find that it is the altered, restructured, Hellenized and disguised form of the Turkish expression "ON-SEKUZUNCUDU" (ON-SEKIZINCIDI) meaning "it is the eighteenth". One of the letter Nís in the Turkish source text has been dropped and the vowels have been altered.
With these findings, we find that the Greek cardinal numeral DEKAOKTW, meaning "eighteen", has been made up from Turkish cardinal numeral "ONSEKIZ" and the Greek ordinal numeral name DEKATOSOGDOOS meaning "eighteenth" has been made up from the Turkish ordinal numeral name ONSEKIZINCIDU, but in a convoluted manner.