https://www.theverge.com/circuitbreaker/2018/10/22/18009410/apple-iphone-xr-xs-max-name-meaning-none

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.)