It’s the greeting, the warning, and the exclamation that defines a city. From South Philly stoops to the steps of the Art Museum, we trace the origins of the two letters that speak for millions.
PHILADELPHIA — If you walk down any street in Philadelphia today, you will hear it. It’s shouted from car windows on Broad Street, whispered between friends in Rittenhouse Square, and barked by construction workers in Kensington.
“Yo.”…