It will depend a little on the place and time, but basically a “Plumassier” or Plume maker was someone who made ornamental feather plumes or sold feathers.
Feather plumes were required for many things from men’s military head dresses to women’s fashion.
Feather-work was big business in the 19th century. It was an age when ladies of fashion changed their outfit three times a day and never went out without a hat. In Paris in the 1890s, it took 800 workshops employing up to 7,000 feather-workers to keep up with the demand. Decline set in with the First World War. By the 1960s, plumassiers were almost as rare as some of the birds they relied on.
In England during the nineteenth century ostrich feather manufacturers were concentrated in a one-mile radius from the City of London into the East End. This was a labour intensive industry and a highly lucrative one too. A high proportion of the workers in this industry were immigrant Jewish women and girls who had experience in the needle trades. In 1883, £500,000 worth of ostrich feathers were imported into London; in 1912, the value of ostrich feathers imported to London from South Africa, with a similar amount imported back out to France, was £2,000,000.