Colin Jost has joked his mother was unimpressed at the name he and Scarlett Johansson chose for their baby.

The Saturday Night Live star and the 36-year-old actress welcomed their son Cosmo into the world last month, but Colin has claimed his mother “didn’t quite understand” the unique name they picked out for their new arrival.

In fact, Colin joked his mother even tried to get them to change it to something else, with the hope the new parents would use Cosmo as a nickname instead.

During an appearance on Late Night with Seth Meyers, he said: My family is very supportive always. My mum, I would say, was slightly thrown by it and didn't quite understand it. I don't know if she thought it was kind of like a hippie thing?

She would call us, after three or four days, she'd be like, 'Cosmo ...' And she'd be like, 'And, now, is it final? Like, did you submit the birth certificate?' And we're like, 'Oh, yeah, we did that at the hospital.’

“She was like 'Oh okay, interesting. Because I was reading that there's also a name Cosimo with an ‘I’ so that could also be an option. Maybe you call him Cosimo, that's his real name, but then you can call him still Cosmo.’ ”

Thankfully, the 39-year-old comedian’s mother eventually warmed up to the name after meeting more people with connections to the unusual moniker.

Colin added: So then, she would call, and she would say, 'I met someone — they said their uncle's name is Cosmo, so it is okay.' And I was like, 'It's locked in.’ ”

Meanwhile, it was recently reported the comedian and the Black Widow star — who is also mother to six-year-old Rose, whom she has with her ex-husband Romain Dauriac — are “madly in love” with their son.

A source said: They are very private but elated over the baby. They are both so happy and madly in love with the baby.

“They wanted this child who will fit right into their lives since they already have her daughter. They are an awesome couple, both talented, smart, and clever. They will be the best parents.

Watch Colin's interview on Late Night with Seth Meyers here:​​​​​​​— BANG SHOWBIZ

Photo: TPG News/Click Photos