The Collaborative International Dictionary of English v.0.48:

Prop \Prop\, v. t. [imp. & p. p. Propped; p. pr. & vb. n.
   Propping.] [Akin to LG. & D. proppen to cram, stuff, thrust
   into, stop, G. pfropfen, Dan. proppe, Sw. proppa; of
   uncertain origin, cf. G. pfropfen to graft, fr. L. propago
   set, layer of a plant, slip, shoot. Cf. 3d. Prop,
   Propagate.]
   To support, or prevent from falling, by placing something
   under or against; as, to prop up a fence or an old building;
   (Fig.) to sustain; to maintain; as, to prop a declining
   state. --Shak.
   [1913 Webster]

         Till the bright mountains prop the incumbent sky.
                                                  --Pope.
   [1913 Webster]

         For being not propp'd by ancestry.       --Shak.
   [1913 Webster]

         I prop myself upon those few supports that are left me.
                                                  --Pope.
   [1913 Webster]