This is characteristic of the "Southern drawl" of Southern American English, where the short front vowels have developed a glide up to [j], and then in some areas back down to schwa: pat[pæjət], pet[pɛjət], pit[pɪjət].
Proto-Germanic stressed short i, e, æ become ie,eo, ea regularly in Old English when followed by h or by r, l + another consonant, and long "i, e, æ" become "îo, êo, êa" before "h"
Examples are:
PG *fallan > feallan "fall"
PG *erþō > eorþe "earth"
Reference: Robert B. Howell 1991. Old English breaking and its Germanic analogues (Linguistische Arbeiten, 253.). Tübingen: Max Niemeyer
According to some scholars,[1] the diphthongisation of e is an unconditioned sound change, whereas other scholars speak about epenthesis[2] or umlaut.[3]
Some scholars[4] believe that PIEi, u has a kind of breaking before an original laryngeal in Greek, Armenian and Tocharian, whereas the other Indo-European languages have monophthongs. Typical examples are: