In reply to Heike:
It sounds like a similar story to Sifta's Quid at the Roaches. Dave Salt (Sifta) proclaimed that all the routes that could be done, had been done i.e. the cry of Ichabod: the glory had gone from the Roaches/Scafell/Israel.
John Amies then proved him wrong by finding this innocuous little severe through a tunnel near Piece of Mind. And so named it Sifta's Quid after the bet, although he apparently never received the pound.
So 'Ichabod' is either a joke poked at the previous guidebook editor, or, it's a route named in misunderstanding of not what is meant by "the cry of Ichabod" but in how it is perceived. It could be taken as someone shouting 'Ichabod' as oppose to being shouted by Ichabod. It is most likely that the first ascentionist got all of this and was simply being clever with his route naming.