Word Origin & History
the letter is a late modification of Roman -i-, originally a scribal creation in continental M.L. to distinguish small -i- in cursive writing from the strokes of other letters, especially in the final positions of words. But in Eng., -y- was used for this, and -j- was introduced c.1600-1640 to take up
the consonantal sound that had evolved from -i- since L.L. times. This usage first was attested in Sp., where it was in place before 1600. Eng. dictionaries continued to lump together words beginning in -i- and -j- until 19c.