Green’s Dictionary of Slang

edad! excl.

God!

1675		Woman Turn’d Bully IV i: Edad, I’ll go and put on a clean pair of Sleeves.
c.1681		E. Hickeringill Trimmers Friendly Debate in Works (1709) I 386: Oh! ho! I begin to understumble you, Edad, I will not tell you.
1730		J. Gay Wife of Bath (rev. edn) I xiv: Idad, I believe the little runner would fain be adrift again.
1843		R. Carlton New Purchase I 179: I dad! if I didn’t snatch up Ruff and kiss him!