Mariel is a municipality and town in the Artemisa province of Cuba. It is where the port of Mariel is located, it's the closest port to the United States. The port is known for the Mariel boatlift; a mass emigration of Cuban refugees who fled Castro's dictatorship and traveled from Cuba's Mariel Harbor to the United States between April, 15th and October, 31st 1980. Hundreds of thousands of Cubans boarded fish and shrimp vessels, crossed the treacherous Florida Straits and arrived at U.S. shores. Those involved became known as "Marielitos". By October, 31st 1980 125,266 Cubans and about 25,000 Haitians had arrived to the coast of Florida.Earnest Hemingway named his daughter after the town of Mariel. I've never met any Spanish speaker with this name though, including Cubans. The feminine version would be Mariela, which is fairly common.
Sources:
• https://forebears.io/forenames/mariel (top countries: the Philippines, Argentina, Mexico, US)
• https://www.linkedin.com/search/results/people/?firstName=mariel (top countries: US, Argentina, the Philippines, Mexico)