Green’s Dictionary of Slang

a general oath, lit. ‘God’s hooks’ (cf. cotso! excl.).

1705–07		N. Ward Hudibras Redivivus I:1 24: I trudg’d along as fast, Cotzooks, / As Porter with a Billet Doux.
1709		‘Poem on the Taking of St. Mary’s’ Collection of Eng. Poetry II (1716) 7: Cotzooks, my Dear, why what’s the meaning?
1731		Beau’s Misc. 51: Cotzooks, my Dear, why, what’s the Meaning?