It took many attempts to work out the spelling of "feral"!
I'd heard it before on wild-life programmes, but normally in the context of a non-indigenous species that was threatening the livelihood of the native species (such as the grey squirrel vs red squirrel in the UK).
I hadn't thought of Googling for a ferrule cat, but when I did, it instantly recognised that I meant "feral" and gave me 3.9MM results!
Most students of history know that the defenestration of Slavata and Martinitz and their secretary was one of the seminal events leading to the Thirty Years War.