Definition of "jakers"

Be jakers, what are they hushing at—and staring at me as if I wor a Roschicrucian.

1838, Charles Dance, “The Irish Lion”, in The Acting National Drama, volume 4, Chapman & Hall, page 75

O jakers, Jenny, says Joe, how short your shirt is!

1922 February, James Joyce, “[Episode 12: Cyclops]”, in Ulysses, Paris: Shakespeare and Company, […]

"Jakers, but we worked." With a long breath she shut her eyes. "But it was too much for one woman and a half-grown girl […] "

2013, Nora Roberts, Irish Thoroughbred‎, Little, Brown, page 25