By the 1940s, the etiquette books were suggesting little more than that the individual in a public setting should make himself as inconspicuous as possible: … Do nothing in company that calls attention to the body or its functions. … Inconspicuousness is the keynote to well-bred behavior in public. … Go your way quietly, taking your place in the crowd unobtrusively, attracting no attention to yourself. … Conduct yourself quietly and unobtrusively. Do not attract attention to yourself and a companion by talking loudly, laughing uproariously, whistling, singing or humming.

Lyn H. Lofland, World of Strangers_ Order a…, loc. 683