Iotacism

[ahy-oh-tuh-siz-uh m] /aɪˈoʊ təˌsɪz əm/

noun
1.
the conversion of other vowel sounds, especially in Modern Greek, into (ē), the sound of iota.
/aɪˈəʊtəˌsɪzəm/
noun
1.
a tendency of vowels and diphthongs, esp in Modern Greek, to acquire the pronunciation of the vowel iota (iː)