Swear Jar is a jar of money. This jar is owned by Manny. If Greg or Rodrick cuss in front of Manny, they will have to give money to him. This idea was thought of by Susan. The jar was made so that Greg and Rodrick wouldn't swear (Even though they did it anyway, causing Manny to become rich). Soon, Greg and Rodrick would make up substitutes for different swears so they wouldn't go broke.