In southernmost Louisiana, where the land on the map looks like grains of rice and okra in a bowl of gumbo, the body of water alongside it has always played a potent role. It has carried in ancestors, allowed for the industries that became the region’s backbone, delivered devastating storms and eroded the coast, lately at an aggressive clip.

Living near the water has required understanding its rhythms and their consequences. But for generations, one thing most people on the Gulf Coast have not thought much about was what to call it.

“It’s always been the Gulf of Mexico,” said Kenneth Armand, 62, standing outside his home in tiny Cut Off, La., just yards away from Bayou Lafourche, on the state’s southern coast. “Ever since I was born.”

When President Trump issued an executive order last month to rename it the Gulf of America, communities along the coast found themselves thinking about the basin in a way many never had before.

For many Gulf Coast residents, the change was surprising, if not puzzling — the order was unexpected and not exactly responding to a groundswell. Still, many have accepted it, seeing the move as a reflection of how central the body of water is to the country’s identity and economy.

“God’s greatest country!” said Mr. Armand’s wife, Jeanie, 76. “Everybody’s calling it the Gulf of America now.”