Greek kappa, before that Phoenician kaph — "palm of the hand".
K
Latin nearly dropped K entirely: C was doing the job. It survived in a handful of words and came back later with Greek and Germanic borrowings.
Baker · Bakker · Barker · Becker · Black · Brook · Brooks · Clark · Cook · Franklin · Hawkins · Hicks · Jackson · Jenkins
In the modern alphabet this letter is number 11 of 26. Before it comes J, after it L. 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 9 and closes 4. Among the 96 given names in the base it appears in 6. The surname carrying the most of it is Bakker, with 2.
Mark · Patrick · Jack · Frank · Katherine · Kevin
These letters came from the Greek alphabet.