From Nabokov's Lectures on Literature, in his discussion of Bleak House. The scholar is discussing the three types of narrator: the moving pillar, the sifting agent, and the perry.

"The third type is the so-called perry, possibly derived from periscope, despite the double r, or perhaps from parry in vague connection with foil as in fencing. But this does not matter much since anyway I invented the term myself many years ago."