Roughcast or coarse plaster used to coat the exterior walls of buildings, especially in Scotland and Northern England.
From Scottish and Northern English dialect, possibly from Old Norse herils or similar roots meaning 'to drag' or 'rough.' The material earned its name because it's essentially dragged or thrown onto walls in a rough, unfinished manner.
Scottish buildings with their distinctive rough-textured walls aren't just styled that way—'harl' is the actual word Scots use, and it's become so regional that most English speakers have never heard it.
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