Psalm and Kim Kardashian West. Picture: Instagram
Kim Kardashian West says her son Psalm is the "most calm" of her four children and has posted a sweet picture of him.

The 38-year-old reality TV star and her rapper husband Kanye West, 42, welcomed Psalm via a surrogate in May and Kim - who also has children North, six, Saint, three and Chicago, 19 months, with Kanye - shared a sweet picture with Psalm and praised his relaxed personality.

She wrote: "My little man is the sweetest ever! He's honestly the best baby. Sleeps through the night and by far my most calm. How did I get so lucky?"

Kim's mother Kris Jenner previously revealed the inspiration for Psalm's name - which also means "sacred song or hymn" - was the Bible's "Book of Psalms". 

She said: "The inspiration was the 'Book of Psalms' in the Bible."

Kris also admitted the youngster has been "such a blessing" for the showbiz power couple, and described him as "perfect". 

She added: "I think it's just a wonderful way to celebrate how they feel. And he's such a blessing, so it's perfect."

Kris' name inspiration confirmation comes after it was said the couple had "mutually" agreed on the moniker, and that rapper Kanye was "very involved" in the process, as a regular reader of 'Psalms', the third section of the Hebrew Bible. 

A source said: "He and Kim do exactly what every couple does, where they each bring up names and the other one gives their feedback. It's very traditional that way.

"Kanye would never just choose a name that Kim doesn't like, or vice versa. The names are things that they mutually agree upon.

"Kim and Kanye are bursting with happiness over Psalm. He's such an incredibly great baby, and so far, it's been an easy addition to the family...

"Kim and Kanye are both busy with their projects, but have slowed down a bit recently to spend quality time with Psalm."

"The kids instantly fell in love with him. North will always be the one in charge, but she loves her little brother."