Janet and John were the children in my reading books at school.
Not many joining words (conjunctions) begin with J, but it is needed for adjectives, such as jolly, joyful, joyous, jovial, and jammy.
A jammy dodger is a biscuit (cookie) here with jam in the middle of a sandwich.
Jazz is played at a jam session.
Jam sets or jells; it is put in jars.
Plants from Japan are japonicas.
Jugglers juggle juggling balls.
Jeremiah, Josiah and other J.’s are interesting characters in the Bible and a fictionalised version by J. Francis Hudson. “A fortress among my people”.
Joshua at Jericho judged Jehovah’s orders to be judicious. (He just did what he was told!) Joshua 6