Английский Этимологический словарь - leak (v.)

- "to let water in or out" [Johnson], 1440, from M.Du. leken "to drip, to leak," or from O.N. leka, cognate of O.E. leccan (which did not survive into M.E.), all from P.Gmc. *lek- "deficiency." The figurative meaning "come to be known in spite of efforts at concealment" dates from at least 1840; transitive sense first recorded 1859. Sense of "urinate" is from 1930s.