The Argyll one seems to have been named by the soldiers who built the 18th century military road, although it must have had an earlier Gaelic name, because it's one of the very few ways through the hills into Argyll.

These days it's mostly famous for falling down - every so often the road is closed because of a landslide, and most of the rest of the time one lane of it is closed for anti-landslide works!

Pictures of the marker stone and other things at https://ingreatwaters.wordpress.com/2019/03/08/throwback-the-rest-and-be-thankful/ if you are interested :)