Crapaud is a slur used to describe French in a derogatory way. Originally the name of a South European frog, although during the Napoleonic Wars it became a term used by British soldiers referring to their French enemy.
The word Crapaud is a racial slur that has been used historically to degrade and dehumanize french. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to french. If you are unsure about whether or not it is appropriate to use the word Crapaud, it is best to err on the side of caution and avoid using it in any situation.