Definition of "betther"

"Will you, thin?" demanded Pat. "Thin the sooner you do it the betther.

1872, Horatio Alger, Jr., Phil, The Fiddler‎

An' whin ye've been at it an hour ye'll find it goes betther wid a little blasphemin';" and he gave his end of the saw to the reluctant Potts.

1904, Elizabeth Robins (C. E. Raimond), The Magnetic North‎

"'Tis the soldiers have betther treatment than the officers whin it comes to boardin' transports," said the friendly policeman.

1921, Mary Grant Bruce, (Please provide the book title or journal name)‎

Come, gintlemen, show them what’s betther than fifty posts—

1892, William Carleton, Amusing Irish Tales