J-caron

J̌ (minuscule: ǰ) is a letter of the Latin alphabet, derived from J with the addition of a háček. It is used in some phonetic transcription schemes –e.g. ISO 9 –to represent the sound [dʒ]. It is also used in Wakhi in the Latin script, and sometimes in the romanization of Pashto. It is also very often used in romanizations of Classical Mongolian^[1] as a result of the many 20th century European transcribers who would have conflated the sound of a 'j' as read in their native languages with the sound of a 'y' as English speakers would read it, so the j with a caron would have provided a more accurate phonetic transcription to them.

References

1. "Transliteration Systems for Uyghur-Mongolian or Vertical or Old Script". Tibetan and Himalayan Library.