Definition of "hisself"

Among those who seemed disposed to join in this opinion was the Jehu of the Warwickshire coach, who expressed his conviction to our hero, that "he wos a young gent as had much himproved hisself since he tooled him up to the 'Varsity with his guvnor."

1853, Cuthbert Bede [pseudonym; Edward Bradley], “Mr. Verdant Green terminates his existence as an Oxford Freshman”, in The Adventures of Mr. Verdant Green, an Oxford Freshman, London: Nathaniel Cooke, […], page 116

Then when he had finally got through he sat down and luk'd as tho' he hisself would die of grief if they brought in a verdict of guilty.

1897, The Cosmopolitan, volume 22, page 564

I sure hope he don't get hisself hurt one of these days, running his mouth thataway.

1953, James Baldwin, “The Seventh Day”, in Go Tell It on the Mountain (Penguin Classics), London: Penguin Books, published 2001

‘Charles ain't exactly got his feet on the ground. Last week he swore to me that he was spending his nights in New Orleans manwhoring hisself. […] ’

2020, Eoin Colfer, Highfire‎, Hachette