This common term for how we watch films originated perhaps with Mary Devereaux, although Lee Clark Mitchell developed its application to Westerns in particular. When we watch a movie, we watch it through the eye of the camera. What the camera sees is what we see. The camera eye is always from the male perspective simply because the male perspective dominated the original culture of both movie making and movie watching. Even if the cameraman or the cinematographer or the director is female, the point of view of the camera is male. So when the cowboy hero comes onto the screen, the camera gazes at him. It lingers over Clint Eastwood’s or John Wayne’s body, often deliberately panning slowly up and down, taking in the costume but also the body itself. We gaze in admiration. We want to be like him. When, however, the glamorous female lead such as Claudia Cardinale or Raquel Welch comes onto the screen and the camera begins its slow gaze, we look not in admiration, even if we are female, but we look as males and desire to dominate her. The male gaze is so natural that we never even notice it, yet it controls much of the way we interpret the film as a whole.
Historical Dictionary of Westerns in Cinema. Paul Varner. 2012.