Re: Ki, Chi, and "Energy"
It is not THAT obscure. The modern usage of "ki" in the terms that Japanese martial arts presently refer to it, can be understood from Miura Baien's writings (18th cen.) where he developed the idea in terms quasi-physical, with relics of the mystical, that we are familiar with.
See here for his Genkiron
which addresses "ki" at length. I have found it invaluable to understand a historical body of thought that underlies the modern Japanese usage of "ki" in physical contexts (it has many other and far wider connotative senses):
Thanks for this reference. I saved for reading in detail later.