what is napiers bone?

Answer 1

A set of rods, made of bone or other material, each divided
into nine spaces, and containing the numbers of a column of
the multiplication table; -- a contrivance of Baron Napier,
the inventor of logarithms, for facilitating the operations
of multiplication and division.

Answer 2

In the early 1600s, a Scottish mathematician called John Napier invented a tool called Napier's Bones, which were multiplication tables inscribed on strips of wood or bone.

Napier, who was the Laird of Merchiston, also invented logarithms, which greatly assisted in arithmetic calculations.