The word “catamount” is an abbreviation of “cat of the mountain” or “cat o’ mountain” or even “cat a mountain”. In the past it was often used to refer to any wild cat species but today it is a fanciful name for the puma, which is more commonly referred to as a mountain lion or cougar in America. I think that you will find that almost nobody refers to the puma as a catamount nowadays.
The origin of “cat-of-the-mountain” is the Spanish “gato monte” according to Mel and Fiona Sunquist, the authors of Wild Cats of the World. However, Google translate translates “gat monte” as “mount cat” and directs me to use the Spanish “gato montés” which translates as wildcat. It is interesting therefore that the Spanish might have been mistranslated to mean a mountain cat when it should have meant a wildcat. I am speculating but that is the history of this word as I understand it.
The puma is well known for having more names than any other wild cat species. Theodore Roosevelt summed up the situation in 1901 when he wrote that “no American beast has been the subject of so much loose writing or of such wild fables as the cougar. Even its name is unsettled….”
Other source: Cat World by Dr Desmond Morris and myself.
SOME MORE PAGES ON THE MOUNTAIN LION: