The "Rob Roy" tartan was worn in lieu of the proscribed MacGregor tartan.

The MacGregors claim to be of royal descent. Their motto is Is "s'rioghail mo dhream," meaning "royal is my race." The earliest possessions of the clan were in Glenorchy. For centuries the MacGregors were persecuted. Sir Walter Scott says of the MacGregors: "They were famous for their misfortunes and the indomitable courage with which they maintained themselves as a clan." For over a century, the name was utterly proscribed, and it needed an act of Parliament to annul the suppression of the name. During the period of proscription many of the MacGregors had to change their names. It was in 1774 that the ban was removed. The famous Rob Roy was a MacGregor of Glengyle.

ну, хоть с этим понятно, не пальцем в небо тыкать.