American dress codes seem to grow more lenient by the day. Jeans, sneakers, and T-shirts are ubiquitous among so-called white-collar workers. The taboo against shorts in professional settings, however, has endured. Here in Washington, D.C., the hot, humid summer air feels like a dog’s breath in your face. But legions of male office workers are expected to keep their legs bundled up, even as their female co-workers shiver in the air-conditioned chill. When I exposed my knees at the office recently—I’d biked to work and hadn’t had a chance to change, I swear—I triggered a lively discussion on Slack. I was made to understand that shorts were for children. Why does the no-shorts rule cling so stubbornly to life, like trousers stuck to sweaty thighs in June? No one has a satisfying answer. It might be the most illogical fashion convention still standing. That means its days are probably numbered, and the glorious era of leg liberation is nigh. There was a time when shorts really were for little boys. In the late-Victorian period, British …