What is bode of contention?

I believe you are looking for the phrase "bone of contention". I'm not sure the origin, but I imagine it has something to do with animals fighting over a bone.

that's completely wrong, the phrase is 'bone of contention' but it means to have a problem with someone or something. if i failed to pay back money to an old friend it would always be a bone of contention between us. but it can apply to anything