tréníð (ON) noun

This form of insult was primarily carving a person’s likeness in an obscene position on an upraised post or pole. It was often accompanied by a libellous poem and qualified as a crime subject to outlawry. See GuL ch. 138.

libel by carving on a tree ONorw GuL Tfb
wood-shame OIce Grg Misc 237 Refs:

KLNM s.v.v. nid, offer, tunge ond, ærekrenkelse