After naming his newborn child 'X Æ A-12', Elon Musk has explained that the name is pronounced "X Ash A twelve". On the Joe Rogan podcast, Musk said "X" is just the letter X and "Æ" is pronounced "ash". Musk said "A-12" was his contribution, to honour the Archangel-12, the precursor to SR-71 which he called the "coolest plane ever".