Recently, it was my mother's birthday. But I did not call her, because I forgot. Luckily (for me), my family don't really celebrate birthdays - at least, not on the actual day. Birthdays occur when they're celebrated, so when they're not celebrated, they don't occur. Make sense? I think so!
I call my mother Um. This is not a common thing to call one's mother, even if one is Vietnamese. It is more common to use Me or Ma, or even Vu, which really puts your mum in her place because vu means breast.
When I was young, I knew I was different from the Aboriginal, white, Greek, Italian and Lebanese kids at school, but I did not realise that I was different from other Vietnamese kids, until we talked about our mums. Or asked for soy sauce. These were the two greatest differentiating factors between me and other Viet kids. Perhaps there were a few others.
Um is pronounced like Oom. Or like mmm, but you start with your mouth open. It is sometimes used by Chinese/Viet kids as a title for distant older relatives, the same as Bac in more mainstream Viet. It's a term of distant filial respect. In my father's family, Um means mother. This is to avoid confusion with my father's mother, who was the supreme ruler of my father's (rather extensive) clan. Everyone called my paternal grandmother Ah Ma, and calling anyone else Ma or even Me would have been just too confusing. I guess. Now, my mother is Ma to all her grandkids and Um to all her kids, in-laws included (well, the ones who speak Viet at any rate).
I have a strong recollection of my first "but you're Viet and you're different from me!" experience. I would have been about 6 years old. My Um had sent me to the corner shop to buy some soy sauce. I knew the particular bottle like it was a close friend. (It kind of is, actually. Soy sauce, that is. Steamed white rice and soy sauce, now that's comfort food!) I wandered around and around the narrow aisles, looking for the particular bottle my mother preferred. Eventually, I gave up and went to the counter and asked where they kept yi tam. The woman behind the counter looked at me. There was another woman with a young girl at the counter. The young girl was about my age and she looked over at me like I was some strange specimen, speaking another language.
The woman behind the counter asked me what I wanted and I repeated, yi tam. The other woman said, I think she's Uncle #5*'s daughter. She's after si dau. Si dau is the more common term for soy sauce, but I did not know that at the time. I said (because it was true), I don't know what si dau is. I want yi tam. The other woman's daughter looked at me aghast. You don't know what si dau is? I said to her, No. Why should I? The other woman went and got me a bottle of soy sauce - it was just the bottle I was after. The daughter said, That's si dau. And smartarse me said, No it's not. It's yi tam. We both just looked at each. I thought the girl was very stupid. She must have thought the same of me.
I took that bottle of yi tam home and showed it to my family and told my story about how strange the people were in the corner store. Um laughed and laughed. So did most of my older siblings. Ba too. Everyone laughed at me, and I honestly had no idea why. I learned, shortly afterwards, a salty lesson in diversity.
Um told me all the different names for yi tam and I was astounded. In the north, they tend to call it nuoc tuong (which is rather confusing because it literally translates as sauce water, or if you're being pedantic, water sauce). Some call it si ieu and some si dau. Me? It's yi tam and nothing else (although I will no think you're stupid if you call it si dau. Swear.)
NT and Wandering Chopsticks both expressed curiousity about why I call my mother Um. I'm no good at being brief in my answers, so this is my answer. I am also no good at staying on topic.