Taffy is a slur used to describe Welsh in a derogatory way. The Taff is the name of the river that runs through Cardiff, the capital of Wales. Also from a poem that starts: "Taffy was a Welshman, Taffy was a thief...." Another explanation is that Taffy is based on an English pronuciation of the common Welsh first
The word Taffy is a racial slur that has been used historically to degrade and dehumanize welsh. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to welsh. If you are unsure about whether or not it is appropriate to use the word Taffy, it is best to err on the side of caution and avoid using it in any situation.