1) An unglazed opening in a wall, originally in a defensive wall, designed to allow missiles to be directed at an attacker. From the seventeenth century it was a similar opening in a barn, through which hay or straw could be forked.
1674 did putt them through a loupe hole into his neighbour’s layth, Bolton by Bowland
1686 Paid to Daniell Tailforth for 6 windowes and 4 lowpeholes, Conistone
1722 in a barne ... saw a riding coat ... and hid the same in a loop hole, Heptonstall
1756 went to the far end of the barn and looked through a loup hole, Birstall.