When I was doing my law degree, we were told that pupils would learn the law from their pupil masters at the bar prior to the formalising of legal exams and over a flagon of mead; there may be a shared etymology as some sources claim that 'bar' is derived from an old word for 'room'.
My main point though is that the term 'bar' dates back to at least the 19th century as can be evinced by the number of extant etched glass windows bearing the legends Saloon Bar/Private Bar. Using the term 'bar' as part of UK establishments is a more modern - probably American - affectation though we can rely on our traditional pub names, derived in part due to former levels of illiteracy. Sadly so many of these names are being erased.