Baby in training! Grimes and Elon Musk's newborn X AE A-XII is apparently learning an interesting skill. The new mom posted a photo of her son wearing a T-shirt featuring a word you've probably never heard of before.\nThe Vancouver-born singer posted a snap on her Instagram story that shows a small glimpse of his face including his nose and mouth with his little tongue sticking out.\nAs for attire, the infant is wearing a black shirt with gold writing featuring the phrase "Mentat in Training."\nAccording to Urban Dictionary, a mentat is "a literary reference from Frank Herbert's Dune series describing someone who has been extensively trained to emulate the mental calculating capacity of a computer."\n"Mentats have a tendency to analyze everything as if it were data for a calculation. This term describes someone who over-analyzes every situation."\nGrimes didn't offer any explanation for why she and Musk's son had that shirt on or what exactly the training entails.\nThe image was posted as part of a collection of photos on her story urging her followers to register to vote.\ngrimes | Instagram\nThe two-month-old was born on May 4 and has made a few appearances on his mom's Instagram stories, including an adorable video of him cuddling with his dad.\nAs you'll recall, he was originally born with the name X Æ A-12, but a series of name changes were necessary.\nFirst, the parents had to ditch the numerals in order to comply with California laws, so he became X Æ A-Xii.\nAfter that, an image of his birth certificate revealed that the Æ was a no-go. Now, his legal first name is X, middle name is AE A-XII, and he took Musk's last name.\nThe super-easy pronunciation is actually just said "X Ash A 12" but it seems like both parents enjoy calling him by nicknames.\nGrimes shared that she says "Little X" and Musk revealed in a video that he calls his son "Baby X."