A well-known mathematician passed away recently, and I happened to be in the Trinity College on the day after. As any Cambridge college undoubtedly would, they mourned the loss of a fellow by flying flags at half-mast.
How can I describe this mourning flag in Latin? Is there a set phrase for having a flag below the summit of the pole to express mourning? I want something that would be applicable for the event mentioned above, but it is of course convenient if it applies more broadly. I assume vexillum lugubre would be understood correctly, but I don't recall seeing it or any other phrase in use.
If Wikipedia is to be trusted, the tradition dates back to the 17th century, so I am not expecting ancient attestations. That said, I would never resist if there are any.