Probably from a confusion of Label, a maiden who appears in the English Here Begynneth the Lyfe of Joseph of Armathia as the daughter of the Welsh king who imprisoned Joseph of Arimathea and his followers when they first arrived in Britain. The king was besieged by Mordrain, to whom he offered Labell as a peace offering. Labell and Mordrain married.
She appears in the Lyfe of Joseph of Armathy as Celidoine’s wife.
Sources
Here Begynneth the Lyfe of Joseph of Armathia with a Praysing to Joseph | 1520
The Lyfe of Joseph of Armathy | c. 1350