| Name | Meaning | Gender | Origin |
|---|
| Jazz | The romantic music
| Male | Word |
| Jazzy | Modern variant of Jasmine: combination of Jocelyn and the musical term jazz.
| Female | |
| Jeeves | | Male | Hebrew |
| Jeff | pledge of peace | Male | English |
| Jellicle | | Unisex | Hebrew |
| Jess | Gift | Male | English |
| Jesse James | | Unisex | Hebrew |
| Jester | A fool at medieval courts | Unisex | |
| Jet | A deep black colour. Aircraft engine that propels an aircraft forward by expelling exhaust gases toward the rear. | Male | Mineral |
| Joker | | Male | Hebrew |
| Junior | Youthful person. Used to distinguish son from father where they have the same name | Male | Latin |
| Junior Mint | | Unisex | Hebrew |
| Jynx | Charm, Spell | Unisex | Latin |
| Katie | Variant of Katherine. Pure.
| Female | English |
| Keyboard | | Unisex | |
| Klondike | | Male | Hebrew |
| Korky | | Unisex | |
| Lassie | Girl
| Female | |
| Laurel | Laurel
| Female | Latin |
| Lexi | Greek, feminine form of Alexander, defending men | Female | English |
| Lilly | Lily | Female | English |
| Luna | moon | Female | Latin |
| Macy | from Matthew's land; club | Female | English |
| Maestro | | Male | |
| Magic | Possessing qualities that produce baffling effects | Male | Word |