The labels of this domain is set up to check if DNS resolvers have query name minimzation (RFC 7816 and 9156) from the client-side.
Querying a TXT RR from this second-level domain with the following labels: a.b.qnamemintest.net reveals if the resolver has qmin enabled or not.
This domain was set up for a research project to query a list of open resolvers from three different geographical locations in April 2022.
If your open resolver was used to query this domain, it's because it was included in the Rapid7 UDP port 53 scan of February 2022.