A pea coat is an outer coat, generally of a navy-coloured heavy wool, originally worn by sailors of European and later American navies.

Why do they call it a pea coat?

The Navy states that the term “peacoat” comes from the letter “p,” which, it says, stands for “pilot,” a kind of fabric. ... Most likely, the word comes from the Dutch pijjakker—pij referring to the course twilled cloth and jakker meaning jacket. The design was born in Holland and then spread around the world.

WHAT IS A Pea in fashion?

In a nutshell

A pea coat is a double-breasted, woollen coat with oversized lapels and a collar that stands up to protect the wearer from the elements.