You see, the son has an Irish name, and it's fairly easy to get mixed up with pronunciations if you're not familiar.
It can be an occasionally baffling language for anyone who isn't fluent, but it does produce some lovely names. However, this couple probably should have done a bit more research.
The 23-year-old woman, who is from Ireland, took to Reddit's 'Am I The A**hole' page to explain her dilemma.
She explained how her aunt and uncle lived in Ireland, but moved to England when their son Liam attended university there.
Now, Liam has a four-year-old son of his own, called Oisin.
Instead of pronouncing it 'oh sheen' as it's supposed to be, they've been saying 'oy sin', much like the popular Chinese sauce hoisin.
The woman explained: "Liam grew up in England, married an English girl, and had a son, who's four. For the sake of this post let's say they named him 'Oisin', which is an Irish name that is meant to be pronounced like 'oh sheen', in accordance with the old Gaelic tradition of nothing being pronounced like it's spelt.
"I am in England right now at university. I also have a son, who is three. Liam and I are within about an hour of each other and we had always meant to meet up. Liam suggested that yesterday, on Christmas, when he and his wife take Oisin to the park, that my son and I come and meet them.
"I had met Liam before when we were kids and teens (just a few times), but since Oisin was born we had only texted, so I had never heard Liam pronounce Oisin's name. We went to the park, we met up with them, and I said 'this must be Oisin'.
"Liam asked why I said it like that. I asked what he meant. He said it's pronounced like 'oi sin'. Like hoisin sauce without the h. I tried to move past it, introduced my son, sent the boys off to play."
She continued: "Liam's wife asked about my son's name (also very Irish) and I told her. Liam joked that with all I know about Irish names, it was shocking that I'd mispronounced his son's name so badly. I said something like 'I'm not the one mispronouncing it'."
Then, she got a phone call from Liam's mum and dad.
The post explained: "I said it's really not. They said they were in Ireland until they were 18, so there's no way they could be saying it wrong.
"During this conversation, I also got a message from Liam saying I'd really upset his wife because she's now convinced that they've been calling their son the wrong name his entire life and that she loved his name before she met me."
The post received hundreds of comments, with some pointing out that the parents can pretty much call their kid whatever they want, but others said it's not her fault they'd been saying it wrong.
One person said: "Irish is an entirely separate language with completely different rules to English. I don't understand why that is so hard for people to grasp.
"If people are going to use our language and culture they could at least have the decency to learn how to say it."
Another said: "It's not 'corrected' if you've never heard your name pronounced that way. It's what he's been called his entire life, that's all that matters in a name."
"However, OP is not the a**hole for correcting them when they tried to suggest she was pronouncing it wrong, she was willing to let it go until they insulted her.
"And now the cousin's wife is upset because she doesn't think her child's name is his name anymore? Get over yourself, your child's name is independent of your past. You've been calling him by his name his entire life."
Whatever the case, it's gonna make Christmas gatherings all the more awkward in future.
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