Kirk, in his 'Secret Commonwealth' names a double, such as the Germans call a Doppelgänger, a 'Co-walker'. In the North it is called a Waff and is said to be a death token. Kirk, however, considers it to be one of the fairies, and says (1933 edition, p.69):

They are clearly seen by these Men of the Second Sight to eat at Funeralls (and) Banquets; hence many ofthe Scottish-Irish will not teast Meat at these Meittings, lest they have Communion with, or be poysoned by, them. So are they seen to carrie the Beer or Coffin with the Corps among the midle-earth Men to the Grave. Some men of that exalted Sight (whither by Art or Nature) have told me they have seen at these Meittings a Doubleman, or the Shape of some Man in two places; that is, a superterranean and a subterranean Inhabitant, perfectly resembling one another in all Points, whom he notwithstanding could easily distinguish one from another, by some secret Tockens and Operations, and so go speak to the Man his Neighbour and Familiar, passing by the Apparition or Resemblance of him.

And on the next page he continues:

They call this Reflex-man a Co-walker, every way like the Man, as a Twin-brother and Companion, haunting him as his shadow, as is oft seen and known among Men (resembling the Originall), both before and after the Originall is dead; and wes also often seen of old to enter a Hous, by which the People knew that the Person of that Liknes wes to Visite them within a few days. This Copy, Echo, or living Picture, goes att last to his own Herd.