In the Middle English Sir Perceval of Galles, Acheflour is Arthur’s sister and Percivale’s mother. The Red Knight killed her husband, also named Perceval, which made Acheflour to raise her son on her own. In her attempt to protect him, she made him ignorat of war and knighthood, so that he might avoid the same fate.
Eventually, Perceval left for Arthur’s court. Acheflour went insane and lived in the woods when she mistakenly thought Perceval had been killed. At the end of the romance, however – and in contrast to other Perceval romances in which his mother dies – Perceval found her and Acheflour regains her sanity. She went to live with him and his lover Lufamour.
Her name is probabaly a corruption of Blancheflour (Blancheflor).
Source
Sir Perceval of Galles | Early 14th century