Kourtney Kardashian has finally revealed her new baby's name and it is definitely not Mila. Kardashian and longtime boyfriend Scott Disick welcomed their third child on Dec. 14, the day that the couple's eldest child, Mason, also celebrated his fifth birthday.

When it comes to baby names, Kourtney Kardashian is considered "the trendsetter," The Huffington Post reported. This year, it seemed that Kardashian pick a name, which is not Mila, suitable for a royal as she gave birth to another son. Meanwhile, the 35-year-old reality star is already a mother to 5-year-old Mason and 2-year-old Penelope.

Kourtney Kardashian finally revealed her baby's name on Sunday, Dec. 21 through a social media post. According to Us Weekly, Kardashian posted a photo on Instagram while she was holding the hand of her newborn son named Reign Aston Disick. Since giving birth, Kourtney and the rest of her family have stayed relatively silent on social media.

It is still unclear why Kourtney Kardashian chose the name "Reign," which is definitely not Mila, for her new baby. However, Los Angeles Times thought that Scott Disick's fondness for fancy cards could be behind the unique name. And though the entire Kardashian clan has remained quiet after Reign's birth, third-time dad Scott Disick shared a congratulatory card from Khloe Kardashian's on-and-off boyfriend, French Montana.

Showbiz insiders have been attempting to know the reason behind Kourtney Kardashian's choice for her new baby's name, which is not Mila. In an exclusive report by Hollywood Life, the reality star wanted a strong name to "represent a ruler" and one that could point out that the Kardashians are American royals.

"Kourtney wanted a completely unique name, she wanted him to represent a ruler and Sovereign Disick doesn't have the same ring to it as Reign Disick," the source said. "Plus Kourtney really believes all the talk when people say that the Kardashians are American royalty, so she really took that to heart and wanted her son to continue that legacy."

Although Kourtney Kardashian did not choose the name Mila for her children, baby Reign's name was also quite a struggle for her and 31-year-old Scott, who is also known as Lord Disick.

"They both fought over the name, and Scott really wanted to stick to honoring their fathers, but Kourtney got more adamant that it be unique," the source added.

As Kourtney Kardashian welcomed her third child, E! News reported that it was an "amazing coincidence" as it fell on her eldest son's [Mason] birthday. And with the revelation of her baby's name, which is absolutely not Mila, the Kardashians are indeed "freaking out with joy."