However, the new parents soon changed their mind about their son's name, and face a dilemma in how to break this news to the mother-in-law who now awkwardly has the wrong name inked on her.
"We have just had a baby two weeks ago, and my mother-in-law immediately tattooed our baby boy's name on her arm." the woman wrote.
"However, we have since had a change of heart re the name. What a nightmare!
"We didn't ask her to [get the tattoo] or know she was doing it. It's obviously really sweet of her to do it so that's not the problem, it's more just now we don't want to call him that.
A woman has revealed her mother-in-law got her grandson's name tattooed - but the new parents have changed their mind about their son's nameiStockphoto by Getty Images
There were plenty of comments from fellow Mumsnet users who weighed in to give their opinion on the matter.
One person said: "Can you use that as the middle name so she can just add the "new" first name to the front?"
"Oh yikes. Perhaps she should have waited until you registered baby...," another person wrote: "Erm... can you live with that name or does it just really not work?"
Someone else added: "To be honest she was a bit premature to do it after only 2 weeks but I definitely would not want to upset my MIL so I’d try to find a compromise."
"No way would I keep a name I didn't actually want to use because someone had decided to tattoo it on their body. Use the name you like. She can have laser removal or a cover-up," a fourth person commented.
In a follow-up, the woman admitted the situation is "slight funny" but "feels so bad for her," as she explained why she and her husband decided to change their baby boy's name.
"The name absolutely doesn't work especially as my dad pointed out it sounds like a certain body part that is less than ideal," she added and even considered using the original name as the middle name like commenters on the forum suggested.
"Even as a middle name isn't really an option but we would keep it for her I guess, just not as a first name."
Have your say in our news democracy. Click the upvote icon at the top of the page to help raise this article through the indy100 rankings.