...in more modern-times it became a tapered or 'feather-edge' board
That’s very interesting Sanctuary.
There really is a lot of clapboard around here – some of it very old, and it fits nicely into the East Anglia landscape where stone has always been a scarce building material and rarely seen.
‘Feather-edge’ by the way has moved from an architectural term to one used in paper conservation, where the edge of the paper is pared down or ‘feathered’ in some other way.