Notation from Horikawa's father in his training notes from 1913:
"Apply Aiki here."
Both predating Chris Hein's date reference,
The date of the origin, and it's meaning are much older then this. Josh Lerner (here: http://www.aikiweb.com/forums/showthread.php?t=21929
) Pointed out that Aiki, was a 2nd century BC, Chinese word used to describe parts of religious rituals in Daoist Sexual intercourse.
Now you certainly don't believe that Takeda Sokaku was talking about Dauist sexual practices when he was using the word Aiki, do you? Well that's the oldest reference I've seen, so unless the use of the word changed, that must be what Takeda was talking about....
Or, possibly, language evolves. And the meaning of a word changes over time. What I was pointing out there, is it makes since that what Inoue was saying could very well be the case.