the.com/shiplap

means A type of wooden board milled with a notched edge so each plank overlaps the next, used to cover walls, ceilings, and exteriors with a ridged, weatherproof surface.

from The word is a straightforward compound from shipbuilding: boards were cut to 'lap' over one another — each edge overlapping the next like scales — to keep hulls and later barns and houses watertight. 'Ship' points to its maritime origin, where this overlapping technique kept rain and sea spray from working their way between boards. It sailed from boatyards into barn construction long before it sailed into farmhouse-chic living rooms.