Hi,
Most common middle name for boys is "Văn" (literature, cultural)
Other than that we have "Minh" (light, smart), "Anh" (smart, good looking), "Hoàng" (precious, golden), Bảo (precious). Many more.
Most common middle name for girls is "Thị" (female).
Others are "Kim" (gold), Xuân (spring), Như (as..), Ngọc (precious stone) and other flower names.
Rule:
Usually parents can give their kids two names: home name and school name (real name).
Home name:
Before people believe pretty children with pretty name can be taken by "gods / devils" of sickness or bad luck. So they give kids the urgliest name they can think of so those gods and devils wouldn't pay attention to their kids when parents call them.
Now, people take cute names, "susu", "cat", "rabbit", "piggy" or their favorite Korean celebrities's names. For some ethinical people they even name their kids electronic's branches as "Samsung", "Motorola" or even names in the bible.
SCHOOL NAME (real name)
. According to Ying yang, male names are in odd number, female's in even number.
. It's common to take the two family names of the parents to be the middle name.
. Husband's family way of naming passed down for generations. "Lê Công Anh"(great grandpa)----> Lê Công Hoàng (grandpa) ---> Lê Công Tuấn (papa) ---> Lê Công Khải (child). (family's tree can track back to a thousand year).
. Parents name their kid by something that means something to them (where they first met, their favorite poet, where they conceived the child) or how they wish their kid to become.
Ex: Male:
Khôi, Anh, Tuấn: handsome
Hoàng, Tài, Phú: weathy
Hiếu, Trung, Nghĩa, Ân: loyal, respectful, family oriented.
. Many now like to take a look at numberology before deciding the names for their kids.
Names are carefully choosen. We believe the name makes the fate, the name shows the person. So each part of the name is selected in order to make a harmonious name of Ying and Yang, solidity and flexibility.