To fill in the blanks, the suitable words would be:

1. **dish**
2. **origin**
3. **before**
4. **easy**
5. **special**

So the full text would be:

"This **dish** is called 'nem ran' by northerners and 'cha gio' by southerners. In Ha Noi, the **origin** of 'nem ran' dates back to a time **before** 'cha ca' had not existed. Although it ranks among Vietnam's specialty dishes, 'nem ran' is very **easy** to prepare. Consequently, it has long been preferred food on **special** occasions such as Tet and other family festivities."