裏金

Etymology
From.

Noun

 * 1)  a thin piece of metal attached to the heel of a sandal; a leather sandal with such a metal piece
 * 2) a bribe
 * 3) a slush fund
 * 4) a short blade affixed slightly offset against the cutting edge of a plane
 * 1) a short blade affixed slightly offset against the cutting edge of a plane
 * 1) a short blade affixed slightly offset against the cutting edge of a plane