This is an encoding of non-ascii-characters into ascii, i.e. accessing https://日本語.fluxcoil.net/ in the browser gets possible. The application (like browser) translates 日本語 and then accesses https://xn--wgv71a119e.fluxcoil.net .
### install libidn sudo yum -y install libidn ### convert 日本語 $ idn 日本語 xn--wgv71a119e ### entry in binds zonefile: xn--wgv71a119e CNAME ns1 ### verification if resolving works $ dig +short 日本語.fluxcoil.net ns1.fluxcoil.net. 37.221.196.24