In the realm of strange celebrity baby names, this one takes the cake. Elon Musk and Grimes secretly welcomed their third child together, Techno Mechanicus, according to a new biography about the Tesla founder by Walter Isaacson. To make matters easier, they’ve reportedly nicknamed him, “Tau.” He follows Musk’s other children with Grimes, son X AE A-XII (“X”), 3, and daughter Exa Dark Sideræl (“Y”), 1. Musk also shares six other children with with ex-wife Justine Wilson.