"kyo" means "teaching" or "principle". I realize the Yoshinkan call it ikkajo, but in the Daito-ryu tradition, ikkajo is a group of 30 techniques - of which ippon dori is one - the one from which Aikido's ikkyo is derived.
I like to think of ikkyo as "first principles" (as in Math). Ikkyo contains all the foundational elements and forms the basis of all other Aikido techniques - namely the circle, the square and the triangle. For that reason, it is the "mother" of all Aikido techniques.
The pin is only a small part of the whole teaching of ikkyo. There is so much more to ikkyo than just a pin on the ground.
Agreed on all points, except ikkyo without a pin is an ikkyo-based technique, but not fully ikkyo, in my mind. Again, others might view it differently, but I suspect I am not the only one.