Phoenician shin — "tooth", through Greek sigma.
S
shin was a row of teeth, drawn as W. Greek turned it on its side into Σ, and Latin rounded it into S. Same tooth, three postures.
Adams · Anderson · Andrews · Armstrong · Barnes · Brewster · Brooks · Burns · Casey · Castillo · Chambers · Collins · Contreras · Daniels
In the modern alphabet this letter is number 19 of 26. Before it comes R, after it T. The order itself is inherited: Latin took it from Greek, Greek from Phoenician, and the sequence has survived largely unchanged for about three thousand years. Every rearrangement since has been an insertion, not a reshuffle.
This is a consonant: it sets the hardness of a name and how it meets the next word. In a corpus of 315 surnames this letter opens 26 and closes 54. Among the 96 given names in the base it appears in 21. The surname carrying the most of it is Esposito, with 2.
James · Joseph · Thomas · Charles · Christopher · Steven · Nicholas · Samuel · Sean · Lucas · Sarah · Susan
These letters came from the Greek alphabet.