Green’s Dictionary of Slang

lay n.1

[SE lay, to wager]

a chance.

[UK]Massinger Renegado III iv: It is an euen lay but that you had A Courtier to your Father.
[UK]J. Lacy Old Troop V i: It’s an even lay whether this Farce be a Comedy or a Tragedy.
[UK]Farquhar Beaux’ Strategem III iii: But I dare not put it upon the lay, for fear of being sent for a soldier.
[UK]Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.