The couple announced last month they had become parents to a second child.
“When we were discussing names I thought, ‘I want to want her name’, and I do. I just love it. I wish I was called it myself,” model Williams told Hello! magazine.
“We decided on it ages ago and as soon as we saw her, we knew it suited her. She is so perfect. I am obsessed with her.”
The baby already has a fully-stocked wardrobe.
“Her wardrobe is already quite extensive,” Williams said.
“I hope nobody buys me any more baby clothes because we’ve definitely got enough until she’s 18 months. I couldn’t help myself.”
Their first child, Theodore, was born in September 2018.
Matthews said his daughter’s arrival “was a wonderful moment that I’ll treasure”.
On picking up mother and daughter from hospital the morning after the birth, he said: “The whole thing was alarmingly unstressful. It felt like I was going out to get a coffee.”
He added: “I’ve always really liked the name Margaux for a girl, spelt in the French way – like the wine.
“When people ask what she’s called I always say Gigi Margaux.”
