Montresor refers to a coat of arms. What is a coat of arms? What is the significance of the coat of arms in the story "The Cask of Amontillado"?

The coat
of arms that Montresor describes is so bizarre that it could be entirely imaginary. It is a huge
golden human foot crushing a snake. It is also almost too appropriate for the occasion. The
motto is also almost too appropriate. It may be that Montresor does not have a coat of arms or a
motto at all. And it may be that Fortunato is being malicious when he says, "I forget your
coat of arms." Fortunato may know perfectly well that Montresor does not descend from a
noble line. Montresor is not committing this murder because of his ancestors or their motto. To
suppose this is to negate the validity of the "thousand injuries" that Montresor
mentions at the beginning of the tale. He may be describing a coat of arms and motto he would
like to have. Poe gives many indications that Montresor is not Italian but French, meaning that
he does not have deep roots in Italy like Fortunato. In the third paragraph of the story, where
Montresor writes disparagingly of Italians, this is clear evidence that he is not Italian
himself. This makes him seem like an outsider to older Italian families, and it is a social
handicap as well as a handicap in his business dealings.