Ton-That

Ton-That ( in Hanoi, in Hue and in Saigon; the closest English approximation is "tong-tuk" or "tong-tut".}}) and Tôn Nữ (for female) is a two-character Vietnamese compound surname, originating from the Nguyễn dynasty. It is the surname for members of the imperial family that were not direct first-born descendants of the Emperor, and therefore considered collateral relatives of the Nguyễn dynasty.

This surname was originally ''Tông Thất'' (), which is derived from a Sino-Vietnamese word, meaning "clan members" or "royal family members". The surname was changed to ''Tôn Thất'' () after Thiệu Trị (né: Nguyễn Phúc Miên ''Tông'') became the emperor due to naming taboo. Provided by Wikipedia