The Collaborative International Dictionary of English v.0.48:

Caducity \Ca*du"ci*ty\, n. [LL. caducitas: cf. F. caducit['e].
   See Caducous.]
   Tendency to fall; the feebleness of old age; senility. [R.]
   [1913 Webster]

         [A] jumble of youth and caducity.        --Chesterfield.
   [1913 Webster]