The Star Trek Concordance points out that "Scotty appropriates one beautiful sword, thinking it to be an ancient Scottish claymore. He may never have seen one, however – the sword is a cutlass." The concordance is incorrect as the sword was a basket-hilted broadsword often also referred to as a claymore.
According to the Star Trek Encyclopedia (4th ed., vol. 1, p. 146), the claymore was being used by Scottish Highlanders in the 16th century. This same source described the claymore as a two-handed sword with a double-edged blade.