Green’s Dictionary of Slang

sowkins n.

In exclamations

by my sowkins! (also by my sowks!)

(Irish/Aus.) an excl. of asseveration.

1830		W. Carleton ‘The Hedge School’ in Traits and Stories of Irish Peasantry I (1868) 286: Be me sowks, I’ll make him sup sorrow for that thrick.
1898		J.D. Brayshaw Slum Silhouettes 23: ‘By my sowkins!’ said he, ‘the last toime she kissed me it was wid a flat-iron.’.
1900		Bulletin (Sydney) 19 May 15/2: Decline! by me sowkins, I wouldn’t know how!