Source : Webster's Revised Unabridged Dictionary (1913)

Backlog \Back"log`\, n. [Back, a. + log.]
   A large stick of wood, forming the back of a fire on the
   hearth. [U.S.]

         There was first a backlog, from fifteen to four and
         twenty inches in diameter and five feet long, imbedded
         in the ashes.                            --S. G.
                                                  Goodrich.

Source : WordNet®

backlog
     n 1: an accumulation of jobs not done or materials not processed
          that are yet to be dealt with (especially unfilled
          customer orders for products or services)
     2: large log at the back of a hearth fire [syn: {log}]
     3: something kept back or saved for future use or a special
        purpose [syn: {reserve}, {stockpile}]
     v : accumulate and create a backlog