It's the change in meaning that makes etymology fun. But surely in general words don't get their meaning changed to something non-related? (young person's patois excepted - my generation used to say 'cool', where today they say 'random', 'sick', in fact a new word every year!)

The above dictionary gives also (for rumba)   '-earlier "ostentation, pomp, leadership," perhaps originally "the course of a ship,"' (the latter surviving in english as 'rhumb line' which probably has now been forgotten, as the navy navigates using it's mobile phones.) But the association of the ideas of a course, or journey, and ostentation, and partying makes me think of our Lord Mayor's Show. And then Carnival (some carnivals actually had boat shaped floats, so were literally 'the course of a ship').

And then mankind passing along the road to somewhere or other, stopping occasionally .

Quite a rumbal.