This post got me thinking and I did a quick Google search for it. It turns out you are both right!
Nombre científico (scientific name) : Leo onca.
Otros nombres vulgares (commonly know as): Jaguar. Tigre. Tigre americano. Overo. Tigre overo. Nahuel. Uturunco.
http://www.barrameda.com.ar/animales/yaguaret.htm
It so happens that in the Mapuche civilisation and many other Native American civilisations a Cougar is an American
Tiger. Specifically, in the Mapuche language,
Nahuel means "tiger", the American kind of tiger which is also a Jaguar = cougar.
You can verify this information simply by googling "Tigre Americano"
Hope this helps,
Magia.