Hello!
Chris and Peter are absolutely correct. AIKIDO was a name proposed by the Dai Nippon Butokukai for all arts "aiki" and accepted by
MINORU HIRAI Sensei, Ueshiba's representative at the Butokukai. It was available for use by many arts. The same applies to Aikijujutsu that can be used by many people. I believe also that the name KODOKAN wasn't created by Kano either. If I remember correctly, it was the name of a Temple and it was used by Kano to indicate his style of jujutsu (judo).
On the other side, if we say YOSHINKAI AIKIDO, TOMIKI AIKIDO, SHINSHIN TOITSU AIKIDO or DAITO RYU AIKIJUJUTSU, we are specifying a system or a method which belongs to a style of Aikido. If I have no link with those styles, I can't rightfully claim that I do Yoshinkai, Tomiki, ShinShin Toitsu or DAITO RYU Aikijujutsu...
Best
