Grimes took to Twitter Tuesday night to shed some light on the name of her newborn son with Elon Musk — X Æ A-12 — without ever getting around to its pronunciation.

Apparently, the “X” stands for “the unknown variable,”  “Æ” is the musician’s “elven spelling of Ai (love &/or artificial intelligence),” “A-12” is, as gathered, a reference to the Lockheed A-12, or, in Grimes’ words, the “precursor to [the] SR-17 (our favorite aircraft). No weapons, no defenses, just speed. Great in battle, but non-violent.”

“A=Archangel, my favorite song,” she adds, before wrapping things up with the words “metal rat.” (Your guess is as good as ours.)

Musk also chimed in during family Twitter time Tuesday night, updating fans that the baby was “happy, healthy & cute as a button” in the replies of a tweet about EPA testing for the Tesla Model S from Monday night — the same one in which he announced the child’s birth.

X Æ A-12 is Grimes’ first child. Musk has five sons from his previous marriage to author Justine Wilson, including twins Xavier and Griffin, and triplets Damian, Saxon and Kai.