Why are cougars called cougars?
The name cougar appears to come from a word used by a German geographer, Georg Marcgrave. In 1648 Marcgrave used the word “cuguacuarana” when referring to the puma, which is the word most often used by scientists. The full Latin (scientific) name is: Puma concolor.
I have deliberately taken the first meaning of the word “cougar” – a reference to a large cat – for obvious reasons
Cuguacuarana is a Guarani word. “Guarani” refers to the Guarani people and their language (Tupi-Guarani language family). They are American Indian people of Paraguay and neighouring regions.
The original meaning of “cuguacuarana” is uncertain. The meaning has been made more uncertain by a typographical error made 300 years ago. It is said that Marcgrave incorrectly transcribed the Tupi Indian word, “sassuarana”, to cuguacuarana. That was a major typo!
Cuguacuarana was shortened to “cuguacuara”. Following that adjustment a French naturalist (an expert in nature history), Georges Buffon, called this wild cat a “cuguar”. Buffon wrote about a number of animals that he had never seen!
From there it is a short adjustment to “cougar”, the name probably most often used today by non-scientists. “Mountain lion is also popular with the public. The evolution of the word over almost 400 years is typical of many words of the English language. The starting point for cougar was a word in an entirely foreign language.
The cougar has many different names: puma, mountain lion, catamount and panther. Each has an origin. You can read about the various names on this page (there will be some overlap with this page).

Source: Wild Cats of the World (a great book and highly recommended).
Thanks, Michael.
The Florida Panther is genetically identical to Puma concolor, except for some inbred minor differences in appearances (the crooked-tail, the Romanesque nose). Caused by their interruption of normal routes of travel by human habitation for the last several centuries, cut-off from breeding with the rest of their own kind, and limited populations transferring any minor trait differences to their offspring. This can be proved when about a decade and a half ago the Florida Park Services imported Mountain-Lions/Pumas from Texas to bolster their dwindling populations. If they were a unique species they are no longer that, any offspring now having all the genetics of their original cousins across the Gulf of Mexico. The “endangered” Florida Panther is a unique study in how a government is trying to claim a species “endangered” for land-grabs that were grandfathered-in to residents in the Florida Panther’s stomping grounds (an area rich in shut-down oil-wells no less). Trying to drive humans off of their own lands by declaring a species is unique and endangered, and in the same breath, breeding them with every other Puma concolor that exists on 2 continents. You can’t have it both ways. Interestingly, their greatest battle in trying to keep the endangered Florida Panther alive so they can achieve these land-grabbing goals, is being interfered with by roaming house-cats, whose many deadly feline diseases are killing them off almost as quick as they can replenish themselves or be replenished by Mountain-Lions imported from other regions. It will be a losing battle, on both America continents if house-cat lovers have their way.
Go away, Jim.
Wish I were prompted more to respond. But, still receiving no notifications.
The word cougar is very confusing for me, because there are so many synonyms. I see cougar defined as mountain lion, panther, puma, etc. Is this really the same cat existing in different regions? Or, are each one just sort of a subcategory with their own unique distinctions, making “cougar” a broad term?
Dee, they are all the exactly the same cat species. It just so happened that people gave this cat various names.
The Florida Panther can be distinguished genetically but that does not alter the fact that these various names describe one cat species. There are no subspecies or variations per region except for the Florida puma which looks exactly the same.
Thanks, Michael.