Anyone who has ever learnt more than one European language will be struck by how similar the word for the cat is across the continent. So it may come as a surprise to learn that the origins of the word are ultimately not Indo-European!
Our word today, cat, comes to us from Middle English catte, which was from Old English catt. So far so similar. The Old English term came from a West Germanic word, which was itself from Proto-Germanic *kattuz. And this was formed from a Latin word, cattus, which came into Latin to replace the previously popular term feles, which is of course the source of the word “feline”. But if the word is from Latin, why should I state that it is not Indo-European? The question is, where did Latin get it from?
Well, the precise origins are unclear, but it was most likely of Afro-Asiatic provenance, related to Late Egyptian caute. The word has proved extremely successful, replacing feles and other native terms all across Europe. Today we have Welsh cath, Italian gatto, Spanish gato, Greek γάτα (gata), German Katze, Danish kat, Russian кот (kot), or кошка (koshka), Basque katu, among others.