The letter "J" was the last addition to the modern English alphabet, distinguished from "I" around the early 17th century, though its separation began in the 16th century.
Origins from Latin
In ancient Roman times,
no separate "J" existed; scribes used a lengthened form of "I" (like a swash or tail) at the start of words for consonantal sounds, such as in "IVLIVS" for Julius.
This evolved from the Semitic "yodh" via Phoenician and Greek scripts,
but English initially treated "I" as serving both vowel (/i/) and consonant (/j/, like "yes") roles.
Adoption in English
Italian scholar Gian Giorgio Trissino advocated distinguishing "I" (vowel) from "J" (consonant) in 1524, influencing printing; early English texts like Shakespeare's 1597 "Romeo and Iuliet" or the 1611 King James Bible's "Iesus" used "I" interchangeably.
By the 1629 Bible edition and around 1630-1640, "J" gained its distinct /dʒ/ sound (as in "judge"), borrowed from Romance languages like French and Spanish.