Flow
: to move in a continuous and smooth way
: to move, come, or go continuously in one direction
Art
: something that is created with imagination and skill and that is beautiful or that expresses important ideas or feelings
: works created by artists : paintings, sculptures, etc., that are created to be beautiful or to express important ideas or feelings`
: the methods and skills used for painting, sculpting, drawing, etc.
Although it is relevant and natural to ask oneself when 'flow arts' came to be, the question is as pointless as asking where a circle begins or ends. The whole universe came to be (how, here, is not the question) in the form of a continuous movement. Expanding from point 0 (if even), to the infinite, it has manifested itself in an ordered, geometric way to form the energetic structure of existence.
In this sense, the concept of 'Flow' is closely related to existence itself.
In 'Flow', there is the underlying idea of continuous, potentially infinite movement. Smoothness within that movement leads to it being artful (gracious, beautiful, and effective).
Flow Arts may have been born from the first human using a stick to defend himself, or from the first civilized human who was bored enough to manipulate any given object with the goal to impress other villagers (such as juggling rocks). They were likely present among tribes from around the world, sometimes involving fire or weighted objects.
Flow Arts are closely related to combat, as most of the tools we use today are inspired from weapons of the old. The necessity for survival in earlier stages of civilisation made it mandatory to know how to fight. These weapons, no longer needed on battlefields, came to be used differently and for displays of skill instead of their killing efficiency.
The idea of 'spectacles' and theatre is not the origin of Flow Arts, but is nowadays the predominant facet of such disciplines.