There is a simple reason why mountain lions are called painters. ‘Painter’ is a local American name for the puma (Felis concolor). Many early white settlers to America referred to the puma as the American panther. The word ‘panther‘ was corrupted to ‘painter’. In many rural districts of the mid-western and eastern US this became the usual pronunciation.
The name ‘painter’ for the puma was made famous in 1913 when James Whitcomb Riley wrote: ‘Yes – and painters, prowlin’ ’bout,/ Allus darkest nights. Lay out/ Clost yer cattle. – Great, big red/ Eyes a blazing’ in their head…’