Vlah is a slur used to describe Serbs in a derogatory way. Stayed behind for 500 years. Vlah's are now extinct but the saying still stuck with the Serbs who replaced them.
The word Vlah is a racial slur that has been used historically to degrade and dehumanize serbs. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to serbs. If you are unsure about whether or not it is appropriate to use the word Vlah, it is best to err on the side of caution and avoid using it in any situation.