cá thu

Etymology
The second element is from a language. Compare 🇨🇬.

Curiously, the Pacific saury, also known as the mackerel pike, is called in Vietnamese, corresponding to  (SV: ) in Chinese.

The thu elements in cá thu ("mackerel") and cá thu đao ("mackerel pike") are therefore seemingly unrelated, with the former being a Tai loan, while the latter is the Sino-Vietnamese reading of.

Noun

 * 1)  mackerel