Source : Webster's Revised Unabridged Dictionary (1913)

Tenableness \Ten`a*ble*ness\, n.
   Same as {Tenability}.

Source : WordNet®

tenableness
     n : the quality of being plausible or acceptable to a reasonable
         person; "he questioned the tenability of my claims" [syn:
          {reasonableness}, {tenability}]