When Deasy says in Nestor that he has rebel blood "On the spindle side," he means his mother's side of the family. The expression probably derives from the fact that hand spinning was traditionally women's work, though it has been suggested that the shape of a spindle is responsible. When the word is used again in Aeolus, that shape does seem to be implied.

John Hunt 2022

A spinning wheel of recent manufacture, showing thread passing by one of the whorls of the spindle. Source: www.ashford.co.nz.