'Jove'. As in 'By Jove'. The word now sounds very archaic, but Jove is a two faced Roman God, and so when the expression first originated it may have been more shocking. Shakespeare refers to Jove on one occasion. In Othello I think. Oh, and 'Jesus' is often used as an expletive. I have know people shout 'Jism' when they're angry. It is a slang word for semen.
At a soccer game people shout "Kick it!". It begins with the letter k.
The candy that begins with J is Jelly Beans.
Jump is shouted. It begins with the letter j.
Jade is a color. It begins with J.
Johnstown is a city in Pennsylvania. It begins with the letter J.
A store that begins with the letter J in Michigan is the J Crew store.
No county in the United Kingdom begins with the letter J.
Sheriffs wear a jacket. It begins with the letter j.
At a sporting event you might shout "Keep it up" or "Kick it!" You might yell at your children saying "Knock it off!"
No word in the English language begins with U and ends with J.
Journey is the name of a music group that begins with "J".
Jasmine is a flower. It begins with the letter j.