In literary terms, Nurse Ratched is a flat character, which means she encounters no changes whatsoever throughout the book. She begins as a scheming, manipulative agent of the Combine and remains so at the novel's conclusion. Her depiction resembles the villains of comic books and one-reel film serials in that she asserts arbitrary control simply because she can.
Much of Ratched's character is evident in her name. McMurphy pronounces it "Rat-shed" during an early section of the novel, indicating that she possesses rodent-like qualities of working quietly, quickly, and to the disadvantage of her victims. The reader is reminded that rats were the carriers of the Black Plague during the Middle Ages, and Ratched infects the hospital's orderlies, student nurses, public relations personnel, and patients with her irrational desire for order.
The name Ratched is also a pun of "ratchet," which is a both a verb and a noun for a device that uses a twisting motion to tighten bolts into place. This pun serves a greater metaphorical purpose in Kesey's hands, as Ratched manipulates the patients and twists them to spy on one another or expose each others' weaknesses in group sessions. The ratchet, as critic Ronald Wallace notes, is also "like a ratchet wrench she keeps her patients 'adjusted,' but like a ratchet, a gear in the Combine, she is herself mechanically enmeshed." The most comic reading of her name, however, is as a pun on the word "wretched."
As Chief describes Ratched, she "tends to get real put out if something keeps her outfit from running like a smooth, accurate, precision-made machine. The slightest thing messy or out of kilter or in the way ties her into a little white knot of tight-smiled fury." Chief goes on to describe her as resembling a doll on the outside, but mechanized and steel underneath. Her expressions are always "calculated and mechanical."
The Public Relations man depicts Ratched as "just like a mother," and in terms of such emasculating mothers as Mrs. Bibbit and Mary Louise Bromden elsewhere in the book, this is clearly not meant by Kesey to be a compliment. Indeed, Ratched also emasculates the men on the ward, forcing them to feel like misbehaving little boys, to reveal each others' secrets and to scare them from ever challenging her authority. But she hides her gender from the world by obscuring her large breasts as much as possible behind the sterility of a starched white nurse's uniform.