Greek upsilon, borrowed into Latin for Greek words.
Y
French still calls it i grec, "the Greek i". Latin brought it in specifically to spell borrowed Greek words and never fully naturalised it.
Bailey · Berry · Boyd · Boyer · Bradley · Byrne · Casey · Delaney · Donnelly · Doyle · Dyer · Flynn · Gray · Harvey
In the modern alphabet this letter is number 25 of 26. Before it comes X, after it Z. 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 vowel: the syllable rests on it, and vowels set the rhythm of a name. In a corpus of 315 surnames this letter opens 1 and closes 17. Among the 96 given names in the base it appears in 10. One occurrence per surname is the ceiling: no surname in the corpus repeats this letter.
Anthony · Timothy · Henry · Mary · Emily · Nancy · Ryan · Gregory · Raymond · Amy
These letters came from the Greek alphabet.