Sikke

While this name is strictly masculine in East Frisia and West Frisia, it appears that it can also be a feminine name in North Frisia and Scandinavia (with the same etymological origin).

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- Sikke as an East Frisian name (where it is listed as masculine):
* http://nds.wikipedia.org/wiki/List_vun_plattd%C3%BC%C3%BCtsche_V%C3%B6rnaams (in Low German, but contains East Frisian and North Frisian given names)

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- Sikke as a West Frisian name (where it is listed as masculine):
* see pages 104 and 153 of the book "Fryske foarnammen / Friese voornamen" written by Rienk de Haan
* http://www.meertens.knaw.nl/nvb/naam/is/Sikke (in Dutch)

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- Sikke as a North Frisian and/or Scandinavian name (where it is listed as feminine):
* "Rufnamen auf den Inseln Föhr, Amrum und Sylt von ca. 1600 bis 1900" (weiblich): http://www.amtfa.de/friesVornw.pdf (in German)
* https://www.nordicnames.de/wiki/Sikke (in English).

In the Frisian-speaking world, Sikke is used as a masculine name in West Frisia (located in The Netherlands) only.