It is narrated from Hazrat Aisha (may Allah be pleased with her) that once the Prophet (peace and blessings be upon him) said, "Why do you not adopt a kunya (honorific name)?" She replied, "On whose name should I adopt a kunya?" The Prophet (peace and blessings be upon him) said, "Adopt your kunya after your son (nephew) Abdullah." Thus, her kunya became Umm Abdullah.