What is "iotacism"

Iotacism \I*o"ta*cism\ ([-i]*[=o]"t[.a]*s[i^]z'm), n. [Gr. 'iotakismo`s a laying too much stress upon the iota ([iota]): cf. F. iotacisme. See Iota.] The frequent use of the sound of iota (that of English e in be), as among the modern Greeks; also, confusion from sounding [epsilon], [iota], [eta], [upsilon], [epsilon][iota], etc., like [iota].
--Littr['e].

n. 1 Pronunciation of another vowel or diphthong as [i], or a vowel shift resulting in such pronunciation, especially in Greek. 2 A misspelling resulting from such pronunciation.

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