When I first heard the term “doublet,” it was used in conjunction with Middle Age-era clothing and weaponry. Judging by its name, I assumed that with was some sort of double-edged sword or dagger, which is hardly the case. A doublet is actually a type tight jacket popular in Europe during the mid-17th century.
Originally, the jacket was used as an undergarment to prevent chafing and bruising. As the doublet garnered popularity, the designs became more elaborate until it became common for the doublet to be donned as an outer garment. Although the doublet has long gone out of style, there is a similar jacket, known as a sherwani, that it worn in present day India.