Scotty is a slur used to describe Scottish in a derogatory way. From the Star Trek character of that name.
The word Scotty is a racial slur that has been used historically to degrade and dehumanize scottish. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to scottish. If you are unsure about whether or not it is appropriate to use the word Scotty, it is best to err on the side of caution and avoid using it in any situation.