Leonard Cohen's "Anthem" carries a line about cracks being where light enters. In photography, the aperture is the opening that controls how much light reaches the film.
In therapy, something similar happens: the places where things don't hold together perfectly, where defenses thin out, are often where the most important material comes through.
The name Aperture holds both of those ideas. It comes from my background in black and white darkroom photography, and from a belief that careful attention to what's been kept in shadow is where change begins.