What is a Hay Penny?

By GovMint :

The term "hay penny" is a colloquial way of referring to the half penny, or "ha'penny."  The half-penny was a coin used in various forms in the United Kingdom and its territories that was worth half of a penny. This small denomination was part of the British currency system for centuries. In the United States, the half-cent, which was minted from 1793-1857, is the closest equivalent.

Sources Used:

https://texancultures.utsa.edu/collections-blog/object-coins/