Closed or fastened with a latch; also to grab onto something or understand something quickly.
From Middle English 'lacche,' possibly from Old English 'læccan.' Originally meant to seize or catch, then the meaning narrowed to the mechanical fastening device and its operation.
A baby literally 'latches' onto its mother during nursing—the word captures that gripping action perfectly, which is why the same word works for both doors and infants finding food.
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