Well Chas, the Scottish National Dictionary gives "Of that Ilk!" as "A person so designated who has the same surname as his property or title". Moncreiffe of that Ilk, (oldest family in Perthshire in the same line, for example,) takes his monicker from the Hill of Moncreiffe, later made into a barony of the same name. The examples quoted in Wiki of Anstruther & MacLachlan of that Ilk, are from the place-names of Anstruther & in the case of MacLachlan his address of Castle Lachlan, Strathlachlan. Blair of Blair is also of territorial origin, (no scarcety of places called Blair!) as indeed are the oldest of Scotland's surnames. The Wiki, "Of that Ilks!" examples quoted, is largely a list of places.
Their giving Balfour of Shaws, (a piece of fiction,) is irrelevant RLS well knew that he couldn't use Balfour of that Ilk as that was a place in Fife & the name was taken.
"Pettigrew of that Ilk" implies a place in the Glasgow area so-called. The only one which springs to mind was a department store called Pettigrew's in Sauchiehall Street!
Skoosh.
