Artists who made prints and people who printed books or newspapers used to make square hats for themselves out of large sheets of paper. It was probably to keep warm in cold workshops. They could make a new paper hat easily if one got ink on it.
The artist and typographic designer Eric Gill often wore a printer’s hat. He drew himself wearing one in his self-portrait. Carpenters wore paper hats too. You can see one in an illustration of the Walrus and the Carpenter by John Tenniel for Lewis Carrol’s Through the Looking Glass.