You currently have Gillis listed as being archaic in the Dutch-speaking world, i.e. it is no longer in use. That is incorrect: there are still living Dutch and Belgian bearers of the name, some of which you can find on Facebook and LinkedIn. As such, the name is just rare instead of archaic: [noted -ed]• https://www.meertens.knaw.nl/nvb/naam/is/Gillis (in Dutch; shows the prevalence of the name in the Netherlands in 2014) • http://www.names.be/jongensnamen.html?met=Gillis&sort=beldesc (in Dutch; shows the prevalence of the name in Belgium in 2009) • https://be.linkedin.com/pub/dir/Gillis/+/be-0-Belgi%C3%AB (lists only bearers living in Belgium) • https://nl.linkedin.com/pub/dir/Gillis/+/nl-0-Nederland (lists only bearers living in the Netherlands) • https://www.facebook.com/search/people/?q=gillisAlso, you should know that Gillis is a dutchization of the French name Gilles: • https://www.meertens.knaw.nl/nvb/verklaring/naam/Gillis (in Dutch)In other words: Gillis is not some sort of native Dutch form of (ultimately) Aegidius. The whole structure of the name is alien to Dutch.Besides, Dutch forms of foreign names tend to stay more faithful to the original name or its pronunciation. Due to this, it is usually easy to see what the source name must be. So, actual Dutch forms of Aegidius include Egied and Gied (nearly extinct as independent names), not something unrecognisable like Gillis.
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• https://www.meertens.knaw.nl/nvb/naam/is/Gillis (in Dutch; shows the prevalence of the name in the Netherlands in 2014)
• http://www.names.be/jongensnamen.html?met=Gillis&sort=beldesc (in Dutch; shows the prevalence of the name in Belgium in 2009)
• https://be.linkedin.com/pub/dir/Gillis/+/be-0-Belgi%C3%AB (lists only bearers living in Belgium)
• https://nl.linkedin.com/pub/dir/Gillis/+/nl-0-Nederland (lists only bearers living in the Netherlands)
• https://www.facebook.com/search/people/?q=gillis
Also, you should know that Gillis is a dutchization of the French name Gilles:
• https://www.meertens.knaw.nl/nvb/verklaring/naam/Gillis (in Dutch)
In other words: Gillis is not some sort of native Dutch form of (ultimately) Aegidius. The whole structure of the name is alien to Dutch.
Besides, Dutch forms of foreign names tend to stay more faithful to the original name or its pronunciation. Due to this, it is usually easy to see what the source name must be. So, actual Dutch forms of Aegidius include Egied and Gied (nearly extinct as independent names), not something unrecognisable like Gillis.