De dónde viene el nombre Datsun?

Pues fíjate tú, que de las iniciales de los socios fundadores, en 1914. Anda que no hemos especulado todos alguna vez en si sería algo Japonés, algo del sol, de la tradición asiática o vete tú a saber qué. Lo del SUN está, pero como acompañante de DAT.

Exactamente, la wikipedia dice esto:

"The new car's name was an acronym of the company's partners' family names:
Kenjiro Den (田 健次郎 Den Kenjirō?)
Rokuro Aoyama (青山 禄朗 Aoyama Rokurō?)
Meitaro Takeuchi (竹内 明太郎 Takeuchi Meitarō?).

It was renamed to Kwaishinsha Motorcar Co. in 1918, and again to DAT Motorcar Co. in 1925. DAT Motors built trucks in addition to the DAT and Datsun passenger cars. The vast majority of its output was trucks, as there was almost no consumer market for cars at the time. Beginning in 1918, the first DAT trucks were produced for the military market. It was the low demand of the military market in the 1920s that forced DAT to merge in 1926 with Japan's 2nd most successful truck maker, Jitsuyo Motors".