Green’s Dictionary of Slang

s’elp me Dash! excl.

[SE dash, i.e. –– (cf. dash v.¹)]

a laboured euph. for s’elp me God!

1892		‘F. Anstey’ Voces Populi 246: Blank my blanky eyes if I’d ha’ stirred a blanky foot, s’elp me Dash, I wouldn’t!
1923		J. Manchon Le Slang.