Two origins have been suggested for the Tan surname:
* The surname came from the ancient , which was located in the western part of what is now Shandong Province. During the Spring and Autumn Period, this state was conquered by the neighbouring . The court changed their surname to Tan in remembrance of their defeated homeland, and later prospered in Hunan Province.
* The surname came from the less common surname 談, another with the same pronunciation in Mandarin and Cantonese. In order to avoid the revenge of their enemies, the clan leaders changed it to 譚.
A study by geneticist Yuan Yida has found that people with either of the two Tan surnames are especially concentrated in Hunan Province which would tend to support these accounts. This does not mean that they are the most common surnames in that province.
Romanisation and pronunciation
''Tán'' is the Chinese character's pinyin romanisation in . It is pronounced and romanised differently in different languages and dialects.
*In , it is romanised as ''Taam4'' in Jyutping and ''Tàahm'' in . It can also be romanised as ''Tam''.
*In Taishanese, it may be romanised as ''Tom'', ''Thom'', ''Hom'', ''Ham'', or ''Hum''.
*In Min Nan, it is romanised as ''Th?m'' in POJ.
*In , it is spelt as ''?àm''.
*Patrick Tam Kar Ming
*Patrick Tam Yiu Man