Introduction  Here’s something most people don’t know: the polo shirt didn’t start in America, or even with tennis. It started on the polo fields of Manipur, in Northeast India, in the 19th century. British soldiers there took to the local players’ collared cotton shirts and pinned the collars down so they wouldn’t flap in the wind. That small fix is why your polo has a collar and a placket today.  Fast forward to now, and “polo” isn’t one shirt but several, a family of collared knit shirts that look alike on …