Walk of atonement
A walk of atonement is a punishment in the Seven Kingdoms usually reserved to punish, humiliate and shame a woman publicly for either adultery or whoring. The custom is usually performed as both a punishment and a way to degrade a woman and rob her of her pride and power.
When Tywin Lannister's father Tytos died, Tywin found his father's mistress trying on one of the gowns of his late mother, Jeyne Marbrand. A common-born woman and the daughter of a chandler, the mistress had dominated Tytos utterly, ordering the household knights about, dismissing servants, and helping herself to Jeyne's jewelry. Expelling the mistress from Casterly Rock, Tywin had her stripped naked and forced the sobbing woman to walk through the streets of Lannisport into exile at the docks, confessing to every man she met that she was a thief and a harlot.
A Dance with Dragons
Cersei Lannister is forced to perform a walk of atonement by the High Septon of the Faith of the Seven from the Great Sept of Baelor to the Red Keep. Cersei is shaved of hair from her entire body, then stripped naked. An escort of Warrior's Sons, Poor Fellows, and several septas protect her from the leering and jeering crowds that have flocked to see her shame.
– House Lannister guard regarding Tytos Lannister's second mistress
They think that this will break my pride, that it will make an end to me, but they are wrong.
-Cersei Lannister's thoughts during her walk
- Kevan Lannister after his niece's walk
- Kevan Lannister thinking of Tytos Lannister's second mistress
All the self-seekers who had named themselves her friends and cultivated her favor had abandoned her quickly enough when Tywin had her stripped naked and paraded through Lannisport to the docks, like a common whore. Though no man laid a hand on her, that walk spelled the end of her power. Surely Tywin would never have dreamed that same fate awaited his own golden daughter.