Jelle is used as a masculine name in West Frisia (located in The Netherlands) and East Frisia (located in Germany) - but also here and there in The Netherlands and Germany itself (often by non-Frisian parents that simply have a love for Frisian names).To get a slight idea about the frequency of this name, see the two links below (assuming you know where West Frisia and East Frisia are located in both countries):http://www.meertens.knaw.nl/nvb/naam/is/Jelle (West Frisia)http://gen-evolu.de/vorn.php?fan=Jelle&rel=0 (East Frisia)Note that in the link provided for West Frisia, the popularity rankings listed reflect The Netherlands as a whole, not the province of Friesland (i.e. West Frisia) only. However, some Frisian first names are so typically Frisian, that they are hardly used outside Friesland, so then it *is* possible to get a pretty good idea of how common they are in Friesland. The thing is, though, one would have to be a Dutchman knowledgeable about Frisian names, or a Frisian living in Friesland or elsewhere in The Netherlands, to gauge which Frisian name is hardly used outside Friesland (and thus whether its popularity rankings on the website of The Meertens Instituut mostly reflect those of Friesland). In the case of Jelle, I can tell you that it is very often seen both in and outside of Friesland, so it's impossible to tell from those rankings exactly how common Jelle is in Friesland only. This actually applies to more Frisian names in The Netherlands, since the Dutch have increasingly been adopting Frisian names because of their short, no-nonsense feel (since there is an on-going trend in my country, where parents favour short names that are down-to-earth and uncomplicated), hence Frisian names have been growing in popularity outside Friesland. As a result, it will slowly become increasingly more difficult to tell from popularity rankings whether certain Frisian names are this popular in Friesland only, or also in the rest of the country (since the popularity rankings make no distinction between Friesland and the rest of The Netherlands).