large decorative black flagpole tassel
Historical item made from tail hair (yak, horse, ox, etc.) or dyed hemp, used as a military standard or ornament. Also written 大頭.
emperor's encampment
Historical term for the imperial camp or headquarters. Rare and limited to classical contexts.
In picture scrolls of ancient battlefields, large decorative tassels are depicted swaying on the commander's flag.
In classical war tales, the word 大纛 sometimes refers to the emperor's main camp.
The exact derivation is uncertain. The kanji 纛 means a large banner or its tassel, and 大纛 literally 'great banner/tassel' came to refer to the imperial standard and, by extension, the emperor's encampment.