-o is often used in connected terms like that, even if the original word have different letter in that palce. For example Czecho-Slovakia comes from the word Czechia, or anracho-capitalism, from the word anarchy and so on.
They also defended the legitimate governments of Hungary and Czechoslovakia from imperialist counter-revolutionary activity in 1956 and 1968 respectively.
Dang... I thought for sure when I saw 2500 BC that the answer would be Akkadian... I suppose they didn't last nearly as long as the actual answer, though.