The WHO has noted that the monkeypox virus, originally found in laboratory monkeys, was named in 1958 before current best practices in nomenclature of diseases were created.
They call that isobutane and it is an isomer of butane, but according to these all important rules of nomenclature, it's not actually any sort of butane at all.
All of these are formally classified in the WMO Cloud Atlas: the international manual for cloud identification, which uses a Linnean nomenclature that has been in place since the early 19th Century.