A Dutch cap or Dutch bonnet is a style of woman's hat associated with the various traditional Dutch woman's costumes. Usually made of white cotton or lace, it is sometimes characterized by triangular flaps or wings that turn up on either side. It can resemble some styles of nurse's hat.
Many parts of the Netherlands have their own traditional costumes.
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References
Wearing a Dutch costume Archived 2016-03-08 at the Wayback Machine, instructions for making iconic hat out of paper for a child's dress-up costume. http://www.hvanrossum.com/costume.html ↩
St. Luke's Hospital School of Nursing Historical Review Archived 2020-12-02 at the Wayback Machine, referring to the more usual style of nurse hat as a "traditional Dutch cap". http://slhson.org/history.html ↩