Wait, what the freak is a dibs?

Dibs ... is a common convention used among friends or siblings to reserve or declare full or partial ownership of a community resource, such as a chair or communal food. As an example, when deciding who gets prime seating in front of a television, if there is one chair that is particularly desirable, an interested party can call "dibs" on that chair; as long as no one has previously called the chair, then it is agreed that the caller is entitled to sit there.

[ Dibs - Wikipedia, the free encyclopedia ]

OK, so we now know (since we've all read that wikipedia article) that more rules and thought went into "dibs" then any of us could have cared for, but where does that word come from?

Most writers seize on what seems to be the most relevant older use of dib as a word connected with childhood. This refers to an ancient and very common game known by dozens of other names (jacks, fivestones, knucklebones, hucklebones; pentalithia in classical Rome), though the name dibs is recorded only from the early part of the eighteenth century.

[ Q&A: Dibs ]

Oh, pentalithia! I love that game. Wait, never heard of it. Cool Words points out that pentalithia means five stones. But if it is the pre-cursor to jacks, where did they find the rubber stone?