According to Lamborghini themselves: https://www.lamborghini.com/it-en/news/marcello-gandini-racconta-il-nome-countach-non-solo-tori https://www.lamborghini.co

According to Lamborghini themselves: https://www.lamborghini.com/it-en/news/marcello-gandini-racconta-il-nome-countach-non-solo-tori https://www.lamborghini.com/it-en/news/marcello-gandini-racc... it was just a (most probably very local) common interjection/expletive by a mechanic (from Piedmont) that was chosen half way between a joke and because it sounded not-so-bad in English as well. The literal meaning is "peste o contagio" (pox or contagion or disease) but it is actually used essentially in what would be "perbacco" o "accidenti" (which I believe would be in English "by jove!" or "damn!").