Most people won’t know what Naf Naf means, but they keep coming back for the hummus and falafel. According to research firm Technomic’s ranking of the top 500 restaurant chains in the U.S., Naf Naf Middle Eastern Grill is one of the country’s fastest-growing eateries, with sales that spiked 58% in 2017. In 2018 it grew to 36 units, all company-owned, with two more planned for 2019. Naf Naf actually means “fan the flame” in Hebrew and suggests encouraging friends and family to come together for a meal. But the chain has also had to overcome tragedy when cofounder Sahar...