Frog is a slur used to describe French in a derogatory way. The French are said to laugh like frogs. When they laugh, their adam's apples bulge out of their necks like frogs. Also perhaps from the French delicacy of frog-legs. Another possible derivation is the Fleur-de-Lys displayed on the French king's banner in
The word Frog 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 Frog, it is best to err on the side of caution and avoid using it in any situation.