It is one of the enduring mysteries of our time: in a lineup full of otherwise neatly named products, Apple’s alternative hardware cycle iPhones have always seen an -S appended to their names, going back to the iPhone 3GS in 2009. But the question remains: what does the S actually stand for?

Turns out, mostly nothing — according to Apple’s senior vice president of worldwide marketing Phil Schiller, who told Engadget in an interview that the letters the company picks for its products don’t actually stand for anything at all. That includes this year’s iPhone XS and XS Max, and of course, the puzzlingly named iPhone XR. (The X does stand for 10, though.)

Schiller did go on to explain what the letters meant to him, commenting that “I love cars and things that go fast, and R and S are both letters used to denote sport cars that are really extra special.” (Porsche is fond of appending the letters on its models, and Mercedes Benz has both its R- and S-Class vehicles, for example.)

It hasn’t always been this way. Back when Apple first announced the iPhone 3GS, Schiller himself proudly explained the name as “the S simply stands for speed, because this is the most powerful, fastest iPhone we’ve ever made.”

And when the iPhone 4S rolled around two years later, CEO Tim Cook explained in an interview with Walt Mossberg and Kara Swisher at the D10 conference that the product’s “S” designation there stood for Siri, Apple’s then newly introduced digital assistant.

By the time that the iPhone 5S and 5C came out in 2013, though, Apple had stopped offering explanations for its names, a trend that continued to the iPhone 6S. Interestingly, the iPhone SE did get a name explanation, again by Schiller, who confirmed that it stands for “Special Edition” to journalist Jason Cipriani.

But now, with the XS, XS Max, and XR, we’re back to the alphabetically nihilistic approach where none of these letters actually stand for anything. It’s a curious choice for Apple, a company that usually prides itself on hidden details, as well as for luxury products in general, which often go out of their way to manufacture elaborate stories behind tiny aspects of their brands to further the air of value and history.

But sometimes, it seems an R is just an R. (Or at least, a car)