It is a popular insult "head node" which refers to the male sex. I titled my series as well as it is by plane trees branches after pruning as I would have treated a bit surreal portraits

têtes de noeuds by Bokey Shutter, on Flickr

têtes de noeuds by Bokey Shutter, on Flickr

têtes de noeuds by Bokey Shutter, on Flickr

têtes de noeuds by Bokey Shutter, on Flickr