Eri Seoi Age

Eri = collar, lapel.

Seoi = on the back, in this case, *over* the shoulder.

Age=to lift or raise, from low to high position.

If Nage were used, this would mean "throwing Uke's lapel" not the action of throwing using Uke's collar.

Seoi'age=throwing over the back or shoulder.

Seoi'nage=shoulder throw (as in throwing Uke's shoulder).

Thanks to Russ Ebert, znbd37a@prodigy.com