Re: ikkyo vs ikkajo
I've been told that ikkajo is simply an older way of saying ikkyo. It's use is probably indicative of an instructor who comes from a lineage that goes back to pre-war aikido. Or Daito ryu. You should understand that in Daito ryu, Ikkajo is a collection of waza, not just a single technique. And many of the pre-war students of Ueshiba Sensei recieved catalogues of waza as their "certificates" from Ueshiba...and these catalogues were of Daito ryu waza, and were written in a format that matched Daito ryu licenses (like the Hiden Mokuroku).
Some of our posters that are into linguistics can probably give a more complete answer from that perspective.