Douglas Harper's Etymology Dictionary
I'se
colloquial or dialectal contraction of I shall, attested from 1796.
Usage examples of "i'se".
As he was plunged in these gloomy soliloquies, he heard the tramp of a horse on the other side of his enclosure, and a strong clear bass voice singing with the liveliness inspired by a light heart, Canny Hobbie Elliot, canny Hobbie now, Canny Hobbie Elliot, I'se gang alang wi' you.
But ef yo' all ain't mighty keerful I'll cut down yo' rations, dat's what I'se goin' to do.
Massa Miles call mah gran'pappy in an' say, 'Bob, yo'all is free an' I'se a ruinated man.