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Old English ᵹéap open, wide, spacious, curved, crooked, vaulted, crafty, astute; repr. Original Teuonic. root gaup-, and prob. related to Old Norse
gaupn hollow made by both hands held together, hollow of the foot, two-hands-ful, etc.
(for definition 3)
From: A New English Dictionary on Historical Principles, James Murray, 1888-1933