The Collaborative International Dictionary of English v.0.48:

Quillaia bark \Quil*la"ia bark`\ (Bot.)
   The bark of a rosaceous tree (Quillaja Saponaria), native
   of Chile. The bark is finely laminated, and very heavy with
   alkaline substances, and is used commonly by the Chileans
   instead of soap. Also called soap bark.
   [1913 Webster]