Kim Kardashian West and Kanye West's son's name Psalm is a ''reflection'' of where the couple are ''spiritually''.

The 'Keeping Up with the Kardashians' star and her 'Famous' rapper husband welcomed their fourth child into the world last week, via a surrogate mother, and on Friday (17.05.19), 38-year-old Kim revealed the unique moniker they have chosen to bestow on the new arrival.

Now an insider has revealed that the couple ''mutually'' agreed on the name and that Kanye was ''very involved'' in the process, as a regular reader of Psalms, the religious Book from the Christian Old Testament and name of the third section of the Hebrew Bible.

A source told PEOPLE: ''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.''

The insider continued: ''Psalms is the longest book in the Bible, but Kanye believes that there's a lot of wisdom in them.

''He reads the Psalms a lot. He talks about the Psalms he loves. So on that level, the baby name isn't a surprise.''

They added that Psalm is a ''reflection of where Kanye and Kim are spiritually''.

'Heartless' rapper Kanye is hugely dedicated to his faith, with his weekly Sunday church service hosted in Lost Hills, Los Angeles, which boasts a ''Christian vibe''.

However, Kim recently explained that her spouse's services are intended to be healing for the participants, rather than ''preaching'' about religion.

The 38-year-old reality star said: ''It's honestly more like a healing experience for my husband. It's just music; there's no sermon. It's definitely something he believes in - Jesus - and there's a Christian vibe. But there's no preaching. It's just a very spiritual Christian experience.''

Kim revealed Psalm's name by posting a picture of a text message she was sent by 41-year-old Kanye which included a picture of their son asleep.

The curvaceous beauty - who is also mother to North, five, and Saint, three, whom she carried naturally, and 16-month-old Chicago, who was also born via surrogate - simply wrote: ''Psalm West.''

In the message Kanye had sent her, he wished her a ''beautiful'' Mother's Day - which was celebrated in America last Sunday (12.05.19) - and said they were ''blessed beyond measure'' to have welcomed Psalm into the world.

He wrote: ''Beautiful Mother's Day

''With the arrival of our fourth child

''We are blessed beyond measure

''We have everything we need.''