Six-Weeker is a slur used to describe French in a derogatory way. Derogatory term used by Germans due to the quick collapse of France during WWII.
The word Six-Weeker 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 Six-Weeker, it is best to err on the side of caution and avoid using it in any situation.