I was rereading Stanley Pranin's Aikido Pioneers: Pre-war Era, portions of which he's now published on-line, and I found a couple of fascinating passages:
When I was in my younger days, I really had my doubts about aikido. When I saw what O-Sensei was doing, I doubted whether he was truly strong. Since I was his student I was always being thrown. I didn’t think he was strong, and thought there must be more to aikido than this. I decided to learn some jujutsu or bojutsu [staff art], and so I went to the dojo of Takaji Shimizu.5 There I was taught how to hold the bo. Then Shimizu Sensei came over to me and said, “It’s wrong to hold the bo so lightly. Attack me all out!” So I asked, “Is it really okay to attack?” and executed a quick movement which sent Shimizu Sensei flying. I thought then that aikido was truly wonderful, and after that, I applied myself to training. Kokyu power is tremendous. It’s different from training in jujutsu. If you execute a sharp movement, you can send your partner fiying. Later, when I met Shimizu Sensei at the Metropolitan Police Department, he said, “Shioda, I’m glad to see you.” That’s what happened.
Mr. Inoue was extremely skilled. He was probably even more skilled at aiki than Mr. Tomiki, in fact, because Mr. Tomiki actually came more from a judo background.
I find these passages striking for several reasons. First of all, Shioda, clearly a pre-war student, uses the term "kokyu." And Okumura, who started during the war, mostly with Tomiki Kenji, was one of nidai Doshu's closest advisors, and therefore, one of the architects of post-O-sensei aikido, uses the term "aiki."
The second reason I find this fascinating is that Shioda is describing sending the headmaster of Shindo Muso-ryu jo flying, using kokyu, and clearly differentiates the power he was acquiring from jujutsu (angles, locks and deflections).
Third, the statement about Inoue, whose education was entirely Daito-ryu through his uncle, Morihei. Any innovations he made afterwards were long after Okumura would have seen him. But, Okumura does not say that he was doing something "different" from Tomiki, other than that Tomiki's judo influence may have impeded, in some respects, him ascending to the same heights. And despite where and when and what Inoue sensei learned (this "aiki,"), Okumura is not making a differentiation of that from aikido itself.
I think the sum total of all of this (beyond my post, to be sure) is that kokyu-ryoku was O-sensei's personal interpretation and development of this "thing" called aiki.