Definition of "sody"

Of course, Zury's sody-crackers went in with the rest, an' me an' Zury always ate some anyhow for appearance sake.

1889, “How The Meanest Man Got So Mean, and How Mean He Got”, in Joseph Kirkland, Zury: The Meanest Man in Spring County‎, Boston: Houghton, Mifflin, and Company, page 81

There's a gossoon in me company that did be workin' in a dispinshary that's after tellin' me that bakin' sody in hot wather wid put the comether on yer pains, me poor frind.

1940, Sir James Elliott, The Hundred Years‎, Robert Hale Limited, page 125

'I'm wantin' half a pound of bakin' sody,' whispered Ally Beag with a terrified glance in my direction.

2012 April 5, Lillian Beckwith, The Hills is Lonely: Tales from the Hebrides‎, Pan Macmillan, page 112