Nade is a slur used to describe Canadians in a derogatory way. Shortened form of "Canadian." Nades is a 2v1 game of tennis.
The word Nade is a racial slur that has been used historically to degrade and dehumanize canadians. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to canadians. If you are unsure about whether or not it is appropriate to use the word Nade, it is best to err on the side of caution and avoid using it in any situation.