The term 'of contention MATTER' can be broken down into two words: 'BONE' and 'MATTER'. BONE is a four-letter word which refers to the hard, calcified tissue that makes up the skeleton of most vertebrates. MATTER is a five-letter word which refers to any physical substance, such as air, water, or solid objects. Together, these two words refer to a subject or issue that is being debated or argued about. This could be anything from a political issue to a personal disagreement.