雙 (shuang1) = Two (Pair)
截 (jie2) = Joint Between Two Sections (Connecting Two Ends Together)
棍 (gun4) = Stick (Short Cudgel)
How ‘Shuang Jie Gun’ relates to ‘Nun Cha Ku’ is not entirely clear. It could be that the term ‘Nunchaku’ is an indigenous Okinawan set of words that do not possess any associative Chinese or Japanese ideograms that directly represent their meaning. A comparison of Chinese and Japanese ideograms might be interesting:
1) Chinese ‘雙’ (shuang1) = Japanese ‘ふたつ’ (futatsu) - sounds like ‘Nunchaku’
2) Chinese ‘截’ (jie2) = Japanese ‘たつ’ (tatsu) - sounds like ‘Chaku’
3) Chinese ‘棍’ (gun4) = Japanese ‘つえ’ (tsue) - sounds like ‘Ku’
Perhaps, when these terms are integrated together, the Japanese ideogram ‘つ’ (tsu) is rationalised and reduced in appearance so that the following approximation is arrived at:
a) Chinese ‘雙’ (shuang1) = Japanese ‘ふ’ (fu)
b) Chinese ‘截’ (jie2) = Japanese ‘た’ ta
c) Chinese ‘棍’ (gun4) = Japanese ‘つえ’ (tsue)
This would suggest that the Chinese (双截棍) ‘Shuang Jie Gun’ equates with the Japanese (ふたつえ) ‘Fu Ta Tsue’. When pronounced in the Okinawan dialect - ‘Fu Ta Tsue’ becomes ‘Nun Cha Ku’. I was told by Master Chan Tin Sang (1924-1993) that a similar device was used on the Hakka farms throughout Southern China to harvest rice and clear land of unwanted vegetation. Later, these devices (which sometimes possessed a ‘hinge’ instead of a chain or cord) evolved into the modern versions now common all over the world! We possess very simple figure of eight sets or patterns in our Hakka family style of gongfu - when making use of this device.