Definition of "impotency"

Some were poor by impotency of nature; as young fatherless children, old decrepit persons, idiots, and cripples.

a. 1628 (date written), John Hayward, The Life, and Raigne of King Edward the Sixt, London: […] [Eliot’s Court Press, and J. Lichfield at Oxford?] for Iohn Partridge, […], published 1630