Today, the Marinière is an emblem of the French style thanks to Coco Chanel, Jean-Paul Gautier and others. But originally this garment was reserved for sailors. It was in 1858 that a State ordinance imposed an official costume on board ships. It is said that the stripes made it easier to spot a sailor who had fallen into the water, but in reality, they probably came from a specific weaving technique and an economy of indigo dyeing (very expensive at the time)!
Source : https://fr.petitsfrenchies.com/la-fabuleuse-histoire-de-la-mariniere/