1728, Edward Young, Love of Fame, the Universal Passion, Satire II in The Works of the Reverend Edward Young, London: P. Brown, H. Hill & S. Payne, 1765, Volume I, p. 85,
Almighty vanity! to thee they owe
Their zest of pleasure, and their balm of woe.
1807, Thomas Cogan, An Ethical Treatise on the Passions, Bath: Hazard & Binns, Part 1, Disquisition 1, Chapter 1, Section 1 “On the utility of the Passions and Affections,” p. 51,
Liberality of disposition and conduct gives the highest zest and relish to social intercourse.
(rare) The woody, thick skin enclosing the kernel of a walnut.
(slang, LGBTQ, derogatory) State of being a flamboyant or effeminate homosexual.