No, not weird at all considering we never called our mothers 'mum'!
Just like Granny is not interchangeable with Granmom, or Mom-mom or Bubbie (Jewish), or Nana (Italian, I think). Those are what most people in the NE part of the US call their grandmothers. I never heard anyone use Granny in those parts or even Grandma. It is interesting though isn't it?
I am from PA. My great-grandmother (who I was fortunate to have until I was 32) was always called Granny, to distinguish her from my two grandmothers. My mom's mom was always Grandmom until recently. Now that she is 92, she is often called Grandma. Don't know why.
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(I also call her Troll, which she gets a kick out of, but that's a whole other story.)
My Mom is Mom, but has taken to calling herself "Mum" when she writes cards to us. I also still call her Mommy, or when I'm angry with her, "MOTHER!" My 21 year old niece calls my mother Me-Mom.
DH and I argued about the fact that he refers to me as Mummy to our dog, while I call myself Mommy. He said the dog is Scottish and I live in England, so I am now Mummy.
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