It is also often used to describe the softness of a fabric, especially t shirts and boxer shorts.
When used to describe the softness of a fabric, it is generally, but not always, implied that jerking off with it would be enjoyable and/or soft to the touch.
Teacher: Are any of you students going to buy the school spirit wear t shit?
All male/hermaphrodite students: It depends if they are jo worthy.
Mother: Why is this soft t shirt covered in so many stains?
Boy: Because it’s jo worthy! I’m not going to use sand paper to beat off! Come on now!