Mahjong originated in China and became popular in the US during the 1920s. Justin Sullivan/Getty Images After my millennial cousin convinced me to try mahjong, I'm hooked. It keeps me off my phone and engaged with my friends and family. Now I understand how people can spend hours around a mahjong table without getting bored. A few months ago, if you'd asked me what I knew about mahjong, I probably would have said it's a game older women play, like my grandma, and that I was definitely not i...