In the early lectures of the eighteenth century, now obsolete, we find the following catechism:
Q. Have you any key to the secrets of a Mason?
Q. Where do you keep it?
A. In a bone box, that neither opens nor shuts but with ivory keys.
The bone box is the mouth, the ivory keys the teeth.
And the key to the secrets is afterward said to be the tongue.
These questions were simply used as tests, and were subsequently varied. In a later lecture it is called the Bone-bone Box.