  Sim\'eon-Denis Poisson was 25 years old when he was appointed Professor of
Mathematics at the \'Ecole Polytechnique in 1806. Elected to the Paris
Acad\'emie des Sciences six years later, he soon became one of its most
influential members. The origin and later developments of the many concepts in
mathematics and physics that bear his name make interesting stories, a few of
which we shall attempt to sketch in this paper.
