The owner, a Chinese (with Canton roots) man born and raised in Ho Chi Minh, had mentioned that he attends a Vietnamese Catholic church. This prompted me to ask him how to say Merry Christmas. He said what sounded like "noen yu ye." I asked him to write it down. He struggled, and then finally asked his wife to come out and write it down. They were discussing the proper spelling as she wrote it. In the end, she came up with:
"Noen vui vẻ."
I was surprised to see "v"'s since I heard [j] or the "y" sound. I Googled the words and they appear to be correct. Could this be because of a Chinese accent? But since he was born there, he shouldn't have one. I didn't pay attention to his Vietnamese wife's pronunciation of it.
On another note, what is the usual Christmas greeting in Vietnamese? Because I got low hits for it on Google.