The Mr Selfridge actress, who gave birth on Tuesday 11 March, revealed to HELLO! the meaning behind her new arrival's moniker.
"Her full name is Orla Rae Kelly Clark," said Katherine. "Making my surname, Kelly, a middle name and Orla is in keeping with the Irish heritage from my side of the family as my dad is Irish."
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"She is a joy already," added Katherine, who gave birth at 7:30pm on Tuesday. "We are cherishing every moment."
Katherine and her husband Ryan Clark welcomed their first child together earlier this week.
The 34-year-old actress – who is perhaps best known for her role on ITV’s Coronation Street - was overwhelmed with happiness when she met her little one on Tuesday.
Her spouse said he was delighted to finally have his daughter in the world, and told fans that Katherine did a great job during labour.
"Katherine has given me the best gift in the world. Absolutely smitten with Orla and so proud of my wife," he said in a statement.
The British star revealed that she was pregnant for the first time last September, following her nuptials in Las Vegas only the month before. “Ryan & I are overjoyed to announce that we are expecting a baby! Feeling very blessed!” she gushed.
Despite being a well-known face, Katherine avoided a lavish ceremony and said “I do” at Sin City’s Little Church of the West after a three year relationship with Ryan. She has claimed in the past that she is a big fan of weddings, but has never been drawn to having an over-the-top one for herself because of the pressure to get everything right.