周书
The Chinese Book of Zhou (7th century) presents an etymology of the name "Turk" as derived from 'helmet', explaining that this name comes from the shape of a mountain where they worked in the Altai Mountains. Hungarian scholar András Róna-Tas (1991) pointed to a Khotanese-Saka word, "tturakä" 'lid', semantically stretchable to 'helmet', as a possible source for this folk etymology, yet Golden thinks this connection requires more data.