Property simply means what is proper to you, in the French sense of what rightfully (and properly) belongs to you (ce qui m'est propre).
Your body properly belongs to you and land (and its fruits) that has been occupied and cultivated by you and your people for generations evidently also properly belong to you.
John Locke justified property in the shape of whatever you mix your labour with, such as picking an apple from a tree in public land, is properly yours.
Thus, for John Locke, building a house on land that does not belong to anyone would mean that house and the land it occupies would be yours in the eyes of Natural Law.
Today, however, property, i.e. exclusive rights to objects, works and land, is acquired largely through money's purchase. Of course in the case of artistic and intellectual productions these by right belong to the creators.
In a Property Law class I attended years ago I came across a definition according to which property is the legally sanctioned right to exclude others from the enjoyment of a thing backed up by the State.
In other words the State is in a position to punish you if you interfere with someone else's property.
Property law is likely the fundamental basis of all man-made law, everything else stemming from it.
And even in the case of Natural Law it is claimed that all natural law rights are in essence property rights and natural law wrongs all different forms of theft of property.
The expression private property is interesting because in its formulation it suggests the notion of privation, i.e. it is your right to deprive others of your private property since, as we saw, property means being able to exclude others because property entails exclusive rights to those things that are proper to you the proprietor.
The fact we still live under money's empire translates in modern forms of property that have nothing to do with land, goods and the body but creations which can be patented or fall under the remit of copyright laws.
In a moneyless and moral community, there would be no desire nor need to have exclusive rights to creations as these would be freely given to be shared among the community's members, contributing to that community's welfare.
It could also be said that in a moral community, a communist commune so to speak, things would be shared equally among its members, not coercively and centrally as in Soviet Bolshevism, but freely and locally because such would be the people's desire, understanding as they do that sharing is caring.
The question of private property, expressed as it can be in the deprivation of others from the enjoyment of land and natural goods that are freely given in the first place, has historically been contentious and indeed continues to be so.
For example Nestlé does not see water as a human right but as something they are entitled to privatise which is to say to deprive others from except in return for monetary compensation (if that).
It does not take a Tolkienesque imagination to see the potential for abuse in so depriving others, e.g. preventing a stream from flowing into lower areas on the grounds that it passes through your bit of land first.
A strong case could also be made that most wars are essentially wars over property, i.e. access to land and natural resources.
A question as to how one could defend one's property in a stateless society is also difficult to answer and is basically the topic of the film Seven Samurai, where a peasant community who get the fruit of their land raided by thieves seek the services of mercenaries to defend them.
Thomas Hobbes justified the State's origins as a contract whereby each relinquishes his personal sovereignty to a Leviathan, Big Brotheresque institution so as to be protected by the latter against being preyed on by other individuals, man being a wolf for man (homo homini lupus est).
Of course this leads to the ridiculous result of statism as being
the brilliant idea that we give a small group of people the right to kidnap, imprison, harass, steal from, and kill people so that we can be protected from people who kidnap, harass, steal and kill people.
It seems to me the question of property is one of the most complex philosophical problems in existence of which I have only scratched the surface in this blog post.