Phoenician resh — "head", through Greek rho.
R
resh drew a head in profile. Greek rho kept it as P; Latin added the leg to tell R from P, and that leg is the whole difference.
Aguilar · Alvarez · Anderson · Andrews · Archer · Armstrong · Arnold · Baker · Bakker · Barker · Barnes · Bauer · Baxter · Becker
In the modern alphabet this letter is number 18 of 26. Before it comes Q, after it S. 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 29 and closes 63. Among the 96 given names in the base it appears in 43. The surname carrying the most of it is Ferrari, with 3.
Robert · Richard · Charles · Christopher · Mark · Andrew · George · Edward · Eric · Alexander · Patrick · Henry
These letters came from the Greek alphabet.