When I first saw the word, I thought perhaps it meant that people seen through it looked like saints in a window. But as one might be making any expression whatsoever, I suppose that doesn't quite work.

Also I rather like the idea of someone solemnly translating "squint" as "hagioscope," as in "Let's have a hagioscope at that, shall we?" or "Too much hagioscope -- let's take this picture where the sun's not in your eyes."