In 1823, a groundbreaking rainproof overcoat made of a new material was sold in Glasgow. This revolutionary coat, made of “india rubber cloth,” was lighter, odorless, and completely waterproof, a stark contrast to the previous heavy, smelly waterproof clothing made of oiled cotton. The inventor, Charles Macintosh, a Scottish chemist, patented the material and used a secret technique involving naphtha to make the rubber soft and sandwich it between two layers of fabric. The coat quickly gained popularity and became known as Mackintoshes, with an extra K. Over time, improvements were made to the durability of the rubber, and today, the Mackintosh brand is owned by a Japanese company.
https://www.theguardian.com/news/2023/oct/12/history-mackintosh-raincoat-charles-macintosh