Green’s Dictionary of Slang

a mild, if blasphemous, oath, lit. ‘God’s heart’.

1598		Jonson Every Man In his Humour III iii: ’Sheart this is Hero and Leander!
1604		Dekker Honest Whore Pt 1 I v: Sheart! attach vs!
1608		Merry Devil of Edmonton C: Banks, your ale is as a Philistine fox, z’hart theres fire i’th’ taile.
1657		Marlowe Lascivious Queen II iv: Away, s’heart take your raggs.
1672		J. Lacy Old Troop V i: ’Sheart, I’ll complain to your Master.
1677		Behn Rover I:ii: Blunt. Nay, ’Sheartlikins, then thou art past Cure [...] ’Sheartlikins, our Cupids are like the Cooks of the Camp, they can roast or boil a Woman, but they have none of the fine Tricks to set ’em off.
1682		Buckingham Chances IV ii: ’Sheart, What shall I do?
1695		Congreve Love for Love II i: ’S’heart, this fellow was not born with you?
1701		Cibber Love Makes a Man II i: I can’t bear this! ’Sheart, I could cry for Madness!
1708		W. Taverner Maid the Mistress II i: Why you --- ’Sheartlikins, I had like to have sworn.