The Collaborative International Dictionary of English v.0.48:

Piles \Piles\, n. pl. [L. pila a ball. Cf. Pill a medicine.]
   (Med.)
   The small, troublesome tumors or swellings about the anus and
   lower part of the rectum which are technically called
   hemorrhoids. See Hemorrhoids.

   Note: [The singular pile is sometimes used.]
         [1913 Webster]

   Blind piles, hemorrhoids which do not bleed.
      [1913 Webster]