Surtout was a kind of overcoat. A "surtout" was a 17th-century term used to describe a coat worn over another coat, like a waistcoat. Surtout was a new name for it; prior to 1684, it was known as "Suravit" on account of Surhabit (overcoat).[1]
Surtout is also a French term that translates as "above all."[2]