According to Osho, a 'mummy' is merely biological and possessive—she reproduces, projects her ambitions, and clings, creating neurosis. A true 'mother' is spiritual and rare: she loves without imposing, fosters individuality, and helps you discover your own truth—giving birth to your soul. 'Ma' is his playful term for a female disciple, 'afflicted' with Rajneeshitis, i.e., devoted to his path.
A mummy just gives birth and tries to control you; a real mother loves you into your own freedom; ‘Ma’ is Osho’s joking name for his women disciples.