Green’s Dictionary of Slang

(US) an indefinite number of anything.

1839		‘Jim Crow, from Kentucky’ in Jim Crow’s Song-Book 13: In de ninety-’leventh chapter, ob de new Almanack, / Dere it tell you abut de white man and black.
1914		S. Lewis Our Mr Wrenn (1936) 11: To keep track of our seventy-’leven accounts.
2003		Lionesses’ Journal at LiveJournal.com 3 Jul. 🌐 Other than that, there are seventy-’leven other things in progress as usual. And I owe the great revolving world and her dog some e-mail, as usual also.