"Do I not see how God's dear pity creeps All through your frame, and trembles in your mouth? Remember in what grave your mother sleeps,
"Buried in some place far down in the south, Men are forgetting as I speak to you; By her head sever'd in that awful drouth
"Of pity that drew Agravaine's fell blow, I pray you pity! let me not scream out For ever after, when the shrill winds blow
"Through half your castle-locks! let me not shout For ever after in the winter night When you ride out alone! in battle-rout
"Let not my rusting tears make your sword light! Ah! God of mercy, how he turns away!
Guenevere is still looking at Sir Gauwaine and asks whether she can see some pity for her in his face.
She imagines that she can see his mouth trembling and hopes that it's because he pities her and wants to find her not guilty.
She addresses him personally again and reminds him of his dead mother.
She brings up his mother's grave, which is somewhere south of King Arthur's court.
She reminds Gauwaine that his mother had been beheaded because of Agravaine's "fell" (deadly) "blow" with an axe.
(Brain Snack! In Arthurian legend, Agravaine was Gauwaine's brother. When their mother was accused of adultery, Agravaine had her head chopped off. Not a nice son, really. So Guenevere is perhaps bringing up this little tidbit of family history to try to get Gauwaine to see the similarities between her own situation and his mother's. Now back to the poem …)
Having brought up Gauwaine's dead mother, Guenevere begs for his pity, hoping that he won't make her haunt him "in the winter night."
She threatens to haunt him and to make his "sword light" (weak) in battle if he has her condemned to death.
But Gauwaine doesn't seem to pity her. In fact, he "turns away."