Iotacism

Iotacism (Greek:ἰωτακισμός, iotakismos) is the process by which a number of vowels and diphthongs in Ancient Greek converged in pronunciation so that they all sound like iota ([i]) in Modern Greek. In the case of the letter eta specifically, this process is known as itacism (from the resulting pronunciation of the letter's name as [ˈita]).