Dodecanese

before vowels dodec-, word-forming element used in technical compounds of Greek origin, signifying "twelve," from Latinized form of Greek dōdeka "twelve" (short for duodeka), from duo "two" (from PIE root *dwo- "two") + deka "ten" (from PIE root *dekm- "ten"). Compare dozen.

peninsula south of Thrace, from Greek khersonesos "peninsula," etymologically "island connected to the mainland," from khersos "dry land, mainland" + nēsos "island," also "(flooded) land near a river, alluvial land," which is of uncertain origin; traditionally from PIE root sna- "to swim," but this is now generally rejected. "As words for 'island' differ from language to language, [nēsos] is probably an Aegean loan (note that Lat. insula is also of unclear origin)" [Beekes]. Compare isle.

 Greek khersos is perhaps from PIE root *ghers- "to bristle" (see horror (n.)) if the Greek word first referred to "arid, stubbly land, and only later to land in opposition to water" [Beekes].