It seems more probable to me that the name change was to further distinguish and distance Aikido from it's Daito Ryu heritage. While there may have been philosophical reasons for this, I think the motivations were just as much political and financial, if not more so.
Ueshiba was beholden to Takeda to forward a fee for every student he taught DRAJJ to. At some point, I believe, Ueshiba considered what he was doing different enough not to warrant this payment. He changed the name of his art from Daitro Ryu Aiki Jujustsu to Aiki Budo to Aikido. It makes perfect sense that naming conventions for techniques would also change to reflect this difference.
I don't think looking at the kanji for esoteric meaning in the suffix will produce any credible insights.
FYI - according to Mochizuki the technique was called "robuse" originally and the Yoseikan still refer to it as such. This strikes me as odd, since my undrestanding is Aikido's ikkajo/ikkyo technique is actually "ippondori" within DRAJJ. So I'm not sure why it would have been called "robuse." Here is a quote related to that from the Yoseikan NA website:
9. What is the relationship between Yoseikan's robuse and the similar techniques practiced as ikkyo in most other aikido schools?
Mochizuki Minoru Sensei said that when he was studying with Ueshiba Sensei (late 1920's), robuse was the name given to the technique that later became Ikkajo, then Ikkyo after the war. The present ikkyo as taught by most Aikikai (and Aikikai related) teachers is the result of the modifications made by Tohei and Kisshomaru Sensei in order to simplify Aikido and make it available to more people....[edited for length]
Patrick Augé Sensei