'Wool Gathering"

I'm reading a book by Rose Tremain called "Music & Silence". It is historical fiction set in the court of Denmark in the 1600's. This passage appears on page 10:

Queen Sofie ... loved to be rowed in a little boat to an island "and there sit in the sunshine and indulge in secret in her passion for knitting. This activity had been proscribed throughout the land as tending to induce in women an idle trance of mind, in which their proper thoughts would fly away and be replaced by fancy. Men called this state 'wool gathering'. That the wool itself could be fashioned into useful articles of haberdashery such as stockings or night bonnets made them no less superstitiously afraid of the knitting craze. They believed that any knitted night bonnet might contain among its million stitches the longings of their wives that they could never satisfy and which in consequence would give them nightmares of the darkest kind."