Throughout the 1930s and 40s, the marketing team for Lux soap repeatedly warned consumers that if they didn't wash their clothes everyday, they risked having "undie odor". Some details from Suellen Hoy in her book Chasing Dirt: The American Pursuit of Cleanliness
Lever Brothers, the makers of Rinso, Lifebuoy, and Lux soap, revised its advertising copy over the years to reflect the changing cultural meanings of soap itself... In 1916, Lux was "a wonderful new product" for "laundering fine fabrics:; by the mid-twenties it could also preserve "soft, youthful, lovely feminine hands" and, by the early thirties, prevent "undie odor" as well—"She never omits her Daily Bath, yet she wears underthings a SECOND DAY."
Francis Countway, the president of Lever Brothers and the individual most responsible for the "discovery" of body odors and the "stop smelling" ad pitch, was inspired by Listerine's successful advertising campaign against the previously unknown halitosis. Countway and his associates admitted, while Lever Brothers' business boomed, that they cared little "about the opinions of softies who think that the Body and Undie Odor copy is disgusting." They were simply doing their job, "bringing cleanliness into a dirty world."
Lux soap was also responsible for the "undies are gossips"
Wilmington Evening Journal - Feb 9, 1932
Kansas City Star - Apr 24, 1940