Celebrity couple Beyonce and Jay Z had the names of their newborn twins trademarked on Monday. The names of the new music royalty are Rumi Carter and Sir Carter, TMZ reported.

It was the same company, owned by Beyonce and Jay-Z, who is Shawn Corey Carter in real life, which also handled the trademark of the couple’s first child, Blue Ivy. They got the name Rumi from a 13th-century Persian poet, Jalal ad-Din Muhammad Rumi.

Trademarks mostly for baby items

In one of Rumi’s most famous poems, the word “sir” appeared on the third line which read: “But sir, a tornado is coming.” The couple plans to use the trademarked names for fragrances, key chains, strollers, hair ribbons, tote bags, rattles, cosmetics, baby teething rings, mugs, water bottles, playing cards, sports balls, and novelty items.

Other celebrities have also given esoteric names to their children. Apple is the name of Gwyneth Paltrow and Chris Martin’s daughter. Calico is the name Alice Cooper gave to his daughter, The Telegraph reported. Film director David Bowie and his wife Angie named their child Zowie. Four kids were given by their father, the late Frank Zapper, the unique names of Moon Unit, Dweezil, Ahmet, and Diva Muffin.

Not very popular names

People checked the names of the two babies in the list of top 1,000 names for any year since 1900. Both names are not in the top 1,000, however, for 2017, Rumi was ranked #2,956, while Sir was #1,925. There is another daughter of a celebrity, actress Josie Maran, who has the same name of Rumi, but she was born in 2006.

Jay-Z possibly named his son, Sir, after hip-hop artist, Sir the Baptist, one of his favorite rappers. He was the opening act in Beyonce’s 2016 Tidal X 1015 event in October. The rapper recalled that Jay-Z discovered him in 2016 while he was performing “Heaven” at the Budweiser Made in America music festival.

Sir the Baptist was walking behind the stage to return to the dressing room when he saw a golf cart with Jay-Z in it.

The singer told him, “Sir, I love your story and I’m following you. Congratulations on a great set.”

Other fans, however, said they preferred other names for the twins. Among their suggestions were Brooklyn and Houston, Slum Beautiful tweeted. Meanwhile, Ilana Kaplan predicts Blue Ivy, Rumi, Sir, North, and Saint will be the next generation of Marvel superheroes. North and Saint are the children of reality star Kim Kardashian and singer Kanye West.